Optical sheet, surface light source device, and display device

Abstract

To provide an optical sheet that makes it possible to obtain a display device capable of controlling emission of video light in a vertical direction and a horizontal direction.SOLUTION: An optical sheet comprises a base material layer 1, and an optical function layer 2 stacked on one surface of the base material layer. The optical sheet, in a plane view, has a rectangular shape having a pair of first sides extending in a first direction and a pair of second sides extending in a second direction. The optical function layer has: a plurality of light transmission parts 3 each having a predetermined cross section and extending in one direction; and light absorption parts 4 formed between the adjacent light transmission parts. The predetermined cross sections of the light transmission parts are trapezoids, and short upper bases are made to be a light incidence side. When a transmissivity of light in a third direction orthogonal to the first direction and the second direction is assumed to be 100%, a relative transmissivity being a ratio of a transmissivity of light in a direction inclined by ±20° to a first direction side with respect to the third direction is 10% or less. Extending directions of the light transmission parts have an angle of 1.5° or more and 20° or less with respect to the second direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical sheet, a surface light source device, and a display device.

Background Art

[0002] Display devices such as televisions and personal computer monitors include a video source that emits video to be displayed, and an optical sheet that improves the quality of the video light and provides it to the observer side (for example, Patent Documents 1 to 3).

[0003] The emission direction of the video light is often the front and a viewing angle at a predetermined angle up, down, left, and right from the front. As a result, the video projected on the screen can be viewed not only from the front but also from a position having a certain angle. On the other hand, depending on the need such as preventing peeping, the front direction is set as the main emission direction and the viewing angle is restricted. An optical sheet for that purpose is disclosed in, for example, Patent Document 4.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, a display device for the purpose of entertainment, etc. of a person sitting in the passenger seat may be arranged in front of the passenger seat of a vehicle such as an automobile. In such a display device for the passenger seat, it is required to control the emission of video light to the driver side so as not to interfere with the driving by the driver. However, when a conventional optical sheet is mounted on the display device for the passenger seat, when the light transmittance (%) in the front is set to 100%, for example, the relative transmittance, which is the ratio of the light transmittance (%) in the direction inclined by ±30° in the left-right direction from the front, becomes about 10%, and the relative transmittance, which is the ratio of the light transmittance (%) in the direction inclined by ±20° in the left-right direction from the front, becomes about 55%, and the light emission to the driver side can be visually recognized. In the case of a right-hand drive vehicle, the display device for the passenger seat is generally arranged in a direction inclined at least 20° to 30° to the left with respect to the front direction of the driver. Similarly, in the case of a left-hand drive vehicle, the display device for the passenger seat is generally arranged in a direction inclined at least 20° to 30° to the right with respect to the front direction of the driver.

[0006] Fig. 11(a) shows a schematic perspective view of a conventional optical sheet. The optical sheet 90 shown in Fig. 11(a) extends, for example, along one side direction of the sheet (the second direction D2 in Fig. 11(a)), and has a layer (optical function layer 32) in which a light transmitting portion (light transmitting portion 33) and a light absorbing portion (light absorbing portion 34) are alternately arranged in parallel along the sheet surface. Such an optical sheet provides viewing angle control only in the direction orthogonal to the extending direction of the light transmitting portion 33 and the light absorbing portion 34 (the first direction D1 in Fig. 11(a)), and it is difficult to control the viewing angle in the parallel direction (the second direction D2 in Fig. 11(a)). Therefore, as shown in Fig. 11(b), when the optical sheet 90 is used for the display device 100 for the passenger seat, the video light may enter the passenger seat side of the windshield of the vehicle. Therefore, it is also required to control the reflection (in the vertical direction) on the windshield in front of the passenger seat. In Fig. 11(b), members other than the optical sheet of the display device 100 are omitted.

[0007] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide an optical sheet capable of obtaining a display device capable of controlling the emission of image light in the vertical and horizontal directions. Specifically, when used as an optical sheet for a display device disposed in front of the passenger seat of a vehicle, it is an object to provide an optical sheet capable of obtaining a display device capable of controlling the emission of image light toward the driver side and capable of controlling the reflection of image light on the windshield in front of the passenger seat.

Means for Solving the Problems

[0008] An embodiment of the present disclosure is an optical sheet including a base material layer and an optical functional layer laminated on one surface of the base material layer. The optical sheet has a rectangular shape having a pair of first sides extending in a first direction and a pair of second sides extending in a second direction in a plan view. The optical functional layer has a plurality of light transmission portions having a predetermined cross section and extending in one direction, and light absorption portions formed between adjacent light transmission portions. The predetermined cross section of the light transmission portion is trapezoidal, with the short upper base being the light incident side. The relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±20° to the first direction side with respect to the third direction when the transmittance of light in the third direction orthogonal to the first direction and the second direction is 100%, is 10% or less. The extending direction of the light transmission portion has an angle of 1.5° or more and 20° or less with respect to the second direction.

[0009] Other embodiments of the present disclosure are optical sheets including a base material layer and an optical functional layer laminated on one surface of the base material layer, where the base material layer is a resin base material, the optical sheet has a rectangular shape having a pair of first sides extending in a first direction and a pair of second sides extending in a second direction in a plan view, the optical functional layer has a plurality of light transmission portions having a predetermined cross-section and extending in one direction, and light absorption portions formed between adjacent light transmission portions, the predetermined cross-section of the light transmission portions is trapezoidal with a short upper base on the light incident side, the optical sheet is an optical sheet for a display device disposed in front of the passenger seat of a vehicle, and the extending direction of the light transmission portions has an angle of 1.5° or more and 20° or less with respect to the second direction.

[0010] Other embodiments of the present disclosure are surface light source devices including the above-described optical sheet and a light source that emits light incident on the optical sheet.

[0011] Other embodiments of the present disclosure are display devices including the above-described surface light source device and a display panel laminated on the surface light source device.

[0012] Other embodiments of the present disclosure are display devices including an optical sheet and a display panel, where the optical sheet includes a base material layer and an optical functional layer laminated on one surface of the base material layer, the optical functional layer has a plurality of light transmission portions having a predetermined cross-section and extending in one direction, and light absorption portions formed between adjacent light transmission portions, the predetermined cross-section of the light transmission portions is trapezoidal with a short upper base on the light incident side, the optical sheet has a relative transmittance, which is a ratio of the light transmittance in a direction inclined ±20° from the normal direction to the left and right directions when the light transmittance in the normal direction of the main surface of the optical sheet is 100% when the display device is installed, of 10% or less, and the extending direction of the light transmission portions viewed from the normal direction has an angle of 1.5° or more and 20° or less with respect to the vertical direction.

[0013] Another embodiment of the present disclosure is a display device comprising an optical sheet and a display panel, and disposed in front of the passenger seat of a vehicle, wherein the optical sheet comprises a base layer and an optical functional layer laminated on one side of the base layer, the base layer being a resin base material, the optical functional layer having a plurality of light-transmitting portions having a predetermined cross-section and extending in one direction, and light-absorbing portions formed between adjacent light-transmitting portions, the predetermined cross-section of the light-transmitting portions being trapezoidal with a shorter upper base being the light-incident side, and the optical sheet is a display device in which, when the display device is disposed in front of the passenger seat of a vehicle, the extension direction of the light-transmitting portions as viewed from the normal direction of the main surface of the optical sheet forms an angle of 1.5° or more and 20° or less with respect to the vertical direction. Effect of the Invention

[0014] The present disclosure can provide an optical sheet that can provide a display device that can control the emission of image light in the vertical and horizontal directions.Furthermore, the present disclosure can provide an optical sheet that, when used as an optical sheet for a display device placed in front of the passenger seat of a car, can provide a display device that can control the emission of image light toward the driver's side and can control the reflection of image light on the windshield in front of the passenger seat. [Brief description of the drawings]

[0015] [Figure 1] 1 is a schematic perspective view illustrating an optical sheet according to the present disclosure. [Diagram 2] 1 is a schematic cross-sectional view illustrating an optical sheet according to the present disclosure. [Diagram 3] 1 is a schematic plan view illustrating an optical sheet according to the present disclosure. [Figure 4] 1 is a schematic cross-sectional view illustrating an optical sheet according to the present disclosure; [Figure 5] 1 is an exploded perspective view illustrating a display device according to the present disclosure. [Figure 6] 1 is a partial exploded cross-sectional view illustrating a display device according to the present disclosure. [Figure 7] 1 is a partial exploded cross-sectional view illustrating a display device according to the present disclosure. [Figure 8]The schematic diagram of the front of the vehicle interior where the display device of the present disclosure is arranged as a display device for the passenger seat and the front view of the display device. [Figure 9] It is a part of an exploded cross-sectional view illustrating the display device of the present disclosure. [Figure 10] It is a schematic cross-sectional view illustrating the optical sheet of the present disclosure. [Figure 11] It is a schematic perspective view of a conventional optical sheet and a schematic diagram of the front of the vehicle interior where it is arranged as a display device for the passenger seat. [Figure 12] The results of measuring the relative transmittance (in the left-right direction) of the optical sheets of Example 4 and Comparative Example 8, and an observation view of the display devices including the optical sheets of Example 4 and Comparative Example 8. [Figure 13] The results of measuring the relative transmittance (in the up-down direction) of the optical sheets of Example 4 and Comparative Example 8, and an observation view of the display devices including the optical sheets of Example 4 and Comparative Example 8.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings and the like. However, the present disclosure can be implemented in many different aspects and is not to be construed as limited to the description of the embodiments exemplified below. Also, for the purpose of making the description clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual form, but this is merely an example and does not limit the interpretation of the present disclosure. Further, in this specification and each figure, elements that are the same as those described above with respect to the previously shown figures may be given the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0017] In this specification, when expressing the manner of disposing one member on another member, if simply denoted as "above" or "below" without particular notice, it includes both the case where another member is disposed immediately above or below so as to be in contact with a certain member, and the case where another member is disposed above or below a certain member with yet another member interposed therebetween. Further, in this specification, when expressing the manner of disposing one member on the surface of another member, if simply denoted as "on the surface side" or "on the surface" without particular notice, it includes both the case where another member is disposed immediately above or below so as to be in contact with a certain member, and the case where another member is disposed above or below a certain member with yet another member interposed therebetween.

[0018] Hereinafter, the optical sheet, surface light source device, and display device of the present disclosure will be described in detail.

[0019] A-1. Optical Sheet (First Embodiment) The optical sheet of this embodiment is an optical sheet including a base material layer and an optical functional layer laminated on one surface of the base material layer. The optical sheet has a rectangular shape having a pair of first sides extending in a first direction and a pair of second sides extending in a second direction in a plan view. The optical functional layer has a plurality of light transmission portions having a predetermined cross-section and extending in one direction, and light absorption portions formed between adjacent light transmission portions. The predetermined cross-section of the light transmission portion is trapezoidal, with the short upper base being the light incident side. The relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±30° to the first direction side with respect to the third direction when the transmittance of light in the third direction orthogonal to the first direction and the second direction is 100%, is 1% or less. The extending direction of the light transmission portion has an angle of 1.5° or more and 20° or less with respect to the second direction.

[0020] The optical sheet of this embodiment will be described with reference to the drawings. FIG. 1 is a schematic perspective view showing an example of the optical sheet of this embodiment. Further, FIG. 2 shows a cross-sectional view of the optical sheet cut along the line indicated by I-I in FIG. 1. FIG. 3 is a plan view of the optical sheet shown in FIG. 1 as viewed along the direction (-D3 direction) from the base material layer 1 toward the optical functional layer 2. FIG. 4 is an enlarged cross-sectional view of the optical sheet shown in FIG. 2. Among the third directions D3, the direction from the optical functional layer 2 toward the base material layer 1 is defined as the +D3 direction, and the direction from the base material layer 1 toward the optical functional layer 2 is defined as the -D3 direction. FIGS. 1 to 3 also show the directions (vertical direction and horizontal direction) in the posture in which the display device is installed when the optical sheet is used in the display device, but the installation posture is not limited to this. For example, when the optical sheet is used in the display device, as shown in FIG. 1, it is preferable that the display device is arranged in a posture such that the first direction D1 is the horizontal direction and the second direction D2 is the vertical direction, but it is not limited to this posture. Hereinafter, each member will be described.

[0021] As shown in FIGS. 1 to 4, the optical sheet 10A of this embodiment includes a base material layer 1 formed in a sheet shape and an optical functional layer 2 provided on one surface of the base material layer 1. The base material layer 1 and the optical functional layer 2 are laminated along the third direction D3. Further, as shown in FIG. 3, the optical sheet 10A in this embodiment has a rectangular shape having a pair of first sides L1 extending in the first direction D1 and a pair of second sides L2 extending in the second direction D2 in plan view.

[0022] The optical functional layer 2 has a plurality of light transmission portions 3 having a predetermined cross-section and extending in one direction, and light absorption portions 4 formed between adjacent light transmission portions 3. As shown in FIG. 2, the cross-section of the light transmission portion 3 cut along the D1-D3 plane is trapezoidal, and the short upper base is the light incident side (light source side). In this embodiment, as shown in FIG. 2, when the light transmittance in the third direction D3 is 100%, the relative transmittance, which is the ratio of the light transmittance in the direction inclined by ±30° with respect to the first direction D1 side with respect to the third direction D3, is 1% or less. Further, as shown in FIG. 3, the extending direction of the light transmission portion 3 has an angle θ of 1.5° or more and 20° or less with respect to the second direction D2.

[0023] According to the optical sheet 10A of the present embodiment, when the light transmittance in the third direction D3 is 100%, the relative transmittance, which is the ratio of the light transmittance in the direction inclined by ±30° to the first direction side with respect to the third direction D3, is equal to or less than a predetermined value. Therefore, it is possible to control the light emission angle in the first direction D1. Further, in a state where the light emission angle in the first direction D1 is controlled, since the extending direction of the light transmission portion 3 has an angle θ of 1.5° or more and 20° or less with respect to the second direction D2, it is possible to control the light emission angle in the second direction D2. This is because the viewing angle in the first direction D1 has a very narrow characteristic, and when an angle θ of 1.5° or more and 20° or less is provided while maintaining that state, the light transmittance in the second direction D2 rapidly decreases.

[0024] Therefore, when the optical sheet of the present embodiment is used in a display device, it is possible to control the light emission angles in the left - right direction and the up - down direction of the display device. More specifically, when used as an optical sheet for a display device arranged in front of the passenger seat of a vehicle, it is possible to control the emission of video light to the driver side, and it is also possible to control the reflection of video light on the windshield in front of the passenger seat.

[0025] For example, by overlapping and using the conventional optical sheet 90 shown in FIG. 11 in two orthogonal directions, it is conceivable to control the light emission angle in the second direction D2 while controlling the light emission angle in the first direction D1. However, with this method, the light transmittance decreases, and the brightness of the display device decreases.

[0026] On the other hand, according to the optical sheet 10A of the present embodiment, it is possible to control the light emission angle in the second direction D2 while controlling the light emission angle in the first direction D1 with a single sheet. Therefore, it is possible to suppress a reduction in light transmittance.

[0027] 1. Optical functional layer The optical sheet in this embodiment includes a base layer and an optical functional layer laminated on one surface of the base layer, and when the optical sheet is used in a display device, the optical functional layer is disposed on the light source side and the base layer is disposed on the viewer side.

[0028] As shown in Fig. 1, the optical functional layer 2 is a layer laminated on one surface of the base layer 1, and has light-transmitting portions 3 and light-absorbing portions 4 arranged alternately in a first direction D1 along the layer surface. In the cross section shown in Fig. 2, the optical functional layer 2 includes substantially trapezoidal light-transmitting portions 3 and light-absorbing portions 4 formed between two adjacent light-transmitting portions 3 and also having a substantially trapezoidal cross section. Light that enters the optical sheet 10A enters the optical functional layer 2 from a light-incident surface Pin and, with the exception of a portion of the light, exits from a light-exiting surface Pout.

[0029] FIG. 4 is an enlarged view of the cross-sectional view shown in FIG. 2. As shown in FIG. 4, light La that perpendicularly enters the light-transmitting portion 3 of the optical function layer 2 at an incident angle of 0° travels straight through the light-transmitting portion 3 and is emitted from the light-emitting surface Pout. Although not shown, light that perpendicularly enters the light-absorbing portion 4 of the optical function layer 2 at an incident angle of 0° is absorbed by the light-absorbing portion 4 and blocked by the optical function layer 2. Of the light that obliquely enters the light-transmitting portion 3 of the optical function layer 2 at an incident angle greater than 0°, light Lb that enters near the boundary with the light-absorbing portion 4 travels obliquely inside the light-transmitting portion 3 and is emitted from the light-emitting surface Pout without being blocked by the light-absorbing portion 4 adjacent to the light-absorbing portion 4. Therefore, light that enters the light-transmitting portion 3 at an angle greater than the incident angle of this light Lb is blocked by the light-absorbing portion 4, and as a result, the overall light that enters the optical function layer 2 is controlled.

[0030] Among the light that enters obliquely at an incident angle greater than 0° into the light transmission portion 3 of the optical functional layer 2, at least a part of the light Lc that travels obliquely inside the light transmission portion 3 and reaches the side surface of the light absorption portion 4 is reflected by the side surface of the light absorption portion 4, changes its traveling direction to the front direction side and is condensed, and then passes through the light transmission portion 3. At this time, if the refractive index of the light absorption portion 4 is set to be smaller than the refractive index of the light transmission portion 3, the light Lc that reaches the side surface of the light absorption portion 4 at an incident angle equal to or greater than the critical angle is totally reflected without being absorbed by the light absorption portion 4. Therefore, due to the total reflection action, the light transmittance is improved.

[0031] Among the light that enters obliquely at an incident angle greater than 0° into the light transmission portion 3 of the optical functional layer 2, the light Ld that travels obliquely inside the light transmission portion 3 and reaches the side surface of the light absorption portion 4 with an incident angle with respect to the side surface smaller than that of the light Lc is partially reflected at the side surface of the light absorption portion 4, and the rest is absorbed by the light absorption portion 4.

[0032] The light transmission portion 3 is a portion mainly functioning to transmit light. As shown in FIG. 2, in cross-section, it is an element having a substantially trapezoidal cross-sectional shape with a long lower base on the substrate layer 1 side and a short upper base on the opposite side. The light transmission portion 3 maintains this cross-section along the layer surface of the substrate layer 1, extends in one direction (a direction forming an angle θ with respect to the second direction D2), and is arranged at a predetermined interval in a direction different from this extending direction (the first direction D1).

[0033] The relative transmittance of the optical sheet in this embodiment, which is the ratio of the transmittance of light in a direction inclined by ±30° to the first direction side with respect to the third direction when the transmittance of light in the third direction is 100%, is 1% or less. The relative transmittance of the above light is preferably 0.6% or less, and more preferably 0.4% or less.

[0034] Note that the average value of the relative transmittance of light in the direction inclined by -30° and the relative transmittance of light in the direction inclined by +30° is defined as the "relative transmittance of light in the direction inclined by ±30°".

[0035] The relative transmittance, which is the ratio of the light transmittance in a direction tilted ±30° toward the first direction with respect to the third direction when the light transmittance in the third direction is taken as 100%, is determined by the following method.

[0036] (Measurement method) First, without placing an optical sheet, the luminance of light from the surface light source alone in the third direction D3 is measured using a viewing angle characteristic measurement device. An edge-light type surface light source using an LED as a light source is used as the surface light source. Next, a surface light source is placed on the back side (optical functional layer side) of the optical sheet, and the luminance of light transmitted through the optical sheet in the third direction D3 and in a direction tilted ±30° toward the first direction D1 with respect to the third direction D3 are measured on the front side (substrate layer side) of the optical sheet using a viewing angle characteristic measurement device. Next, the ratio of the luminance of light transmitted through the optical sheet in the third direction D3 to the luminance of light from the surface light source alone in the third direction D3 is calculated as the transmittance of light transmitted through the optical sheet in the third direction D3. Similarly, the ratio of the luminance of light transmitted through the direction tilted ±30° toward the first direction D1 with respect to the third direction D3 to the luminance of light from the surface light source alone in the third direction D3 is calculated as the transmittance of light transmitted through the direction tilted ±30° toward the first direction with respect to the third direction. Finally, the relative transmittance is calculated, which is the ratio of the transmittance of light passing through the optical sheet in a direction inclined ±30° toward the first direction D1 relative to the third direction D3, when the transmittance of light passing through the optical sheet in the third direction D3 is set to 100%.

[0037] Transmittance of light transmitted through the optical sheet in the third direction D3 T0 (%) = {(brightness of light emitted from the optical sheet in the third direction D3) / (brightness of light from the surface light source in the third direction D3)} × 100 (%) The transmittance T of light transmitted in a direction inclined ±30° toward the first direction D1 with respect to the third direction D3 30 ((%)={(brightness of light emitted from the optical sheet in a direction inclined ±30° toward the first direction D1 with respect to the third direction D3) / (brightness of light from the surface light source in the third direction D3)}×100(%) ·Relative transmittance (%)=(T 30 / T0)×100(%)

[0038] An optical sheet having such optical characteristics can be obtained by adjusting any one or more of the cross-sectional shapes of the light absorption part and the light transmission part, the refractive indices of the light absorption part and the light transmission part, the incident-side aperture ratio, the height of the light absorption part, the OD value of the light absorption part, etc.

[0039] In the optical sheet of this embodiment, the relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±20° toward the first direction with respect to the third direction when the transmittance of light in the third direction is 100%, is preferably 10% or less, and more preferably 5% or less.

[0040] Note that the average value of the relative transmittance of light in the direction inclined by -20° and the relative transmittance of light in the direction inclined by +20° is defined as the "relative transmittance of light in the direction inclined by ±20°".

[0041] The relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±20° toward the first direction with respect to the third direction when the transmittance of light in the third direction is 100%, is obtained in the same manner as the relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±30° toward the first direction with respect to the third direction when the transmittance of light in the third direction is 100%.

[0042] Also, in the optical sheet of this embodiment, the relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±30° toward the second direction with respect to the third direction when the transmittance of light in the third direction is 100%, may be 32% or less, may be 30% or less, or may be 25% or less.

[0043] The relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±30° toward the second direction with respect to the third direction when the transmittance of light in the third direction is 100%, is obtained in the same manner as the relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±30° toward the first direction with respect to the third direction when the transmittance of light in the third direction is 100%.

[0044] In the present embodiment, the extending direction of the light transmission portion 3 has an angle θ of 1.5° or more and 20° or less with respect to the second direction D2 in a plan view. The angle θ is 1.5° or more, and may be 5° or more, or may be 10° or more. On the other hand, the angle θ is 20° or less, and may be 15° or less. By the angle θ being within the above range, it becomes possible to control the light emission angle in the second direction. When the display device is installed in the posture as shown in FIG. 1, the right side as viewed from the observer is the +D1 direction, and the left side is the -D1 direction. In FIGS. 1 and 3, the light transmission portion 3 has an angle θ on the right side (+D1 side) with respect to the second direction D2. In this case, it is preferable that the left side (-D1 side) is the driver's seat side. On the other hand, the light transmission portion 3 may have an angle θ on the left side (-D1 side) with respect to the second direction D2. In this case, it is preferable that the right side (+D1 side) is the driver's seat side.

[0045] The angle θ is obtained by the following method. First, as illustrated in FIG. 3, the optical sheet 10 is placed so that the extending direction of the light transmission portion 3 is vertical. At this time, the optical sheet may be vertically long or horizontally long. Next, among the angles formed by the vertical side (L2) of the optical sheet 10 and the boundary line BL between the light transmission portion 3 and the light absorption portion 4, the smaller angle is measured. When measuring the above angle, the boundary line BL between the light transmission portion 3 and the light absorption portion 4 on the surfaces of the short upper base of the light transmission portion 3 and the long lower base of the light absorption portion 4 of the optical functional layer 2 is used. Also, as illustrated in FIG. 3, for each of the two vertical sides (L2a, L2b) of the optical sheet 10, the above angle is measured at two locations each, and the arithmetic mean value of the four measurement values is taken as the angle θ.

[0046] An interval (groove) having a substantially trapezoidal cross section is formed between adjacent light transmission portions 3. Therefore, the interval (groove) has a long lower base on the upper base side (opposite to the base material layer 1 side) of the light transmission portion 3 and a short upper base on the lower base side (base material layer 1 side) of the light transmission portion 3, and has a trapezoidal cross section. The light absorption portion 4 is formed by filling necessary materials described later. In FIGS. 1 to 4, adjacent light transmission portions 3 are connected by a sheet-like connecting portion 2a on the long lower base side.

[0047] The light transmitting portion 3 has a refractive index of Nt. Such a light transmitting portion 3 can be formed by curing a composition that constitutes the light transmitting portion. This will be explained in detail later. The value of the refractive index Nt is not particularly limited, and is, for example, 1.50 or more, and preferably 1.54 or more. On the other hand, the value of the refractive index Nt is, for example, 1.65 or less, and preferably 1.60 or less. Specifically, the value of the refractive index Nt is 1.50 or more and 1.65 or less, and preferably 1.54 or more and 1.60 or less. This is because a refractive index difference with the light absorbing portion, which will be described later, can be easily obtained.

[0048] The light absorbing portion 4 functions as a gap formed in the above-mentioned gap (groove) formed between adjacent light transmitting portions 3, and has a cross-sectional shape similar to the cross-sectional shape of the gap. Therefore, the short upper base faces the base layer 1, and the long lower base faces the opposite side from the base layer 1. By orienting the short upper base of the light absorbing portion on the light output surface Pout side, a portion of the light that travels through the light transmitting portion and reaches the side surface of the light absorbing portion, specifically the interface between the light absorbing portion and the light transmitting portion, is reflected and concentrated in the front direction, thereby improving light transmittance.

[0049] The light absorbing portion 4 has a refractive index of Nr and is configured to be able to absorb light. Specifically, light absorbing particles are dispersed in a transparent resin having a refractive index of Nr. The refractive index Nr is preferably smaller than the refractive index Nt of the light transmitting portion 3. By making the refractive index of the light absorbing portion 4 smaller than the refractive index of the light transmitting portion 3 in this way, light incident on the light transmitting portion 3 under specified conditions can be appropriately totally reflected at the interface with the light absorbing portion 4. Furthermore, even when the total reflection conditions are not satisfied, some light is reflected at the interface.

[0050] The value of the refractive index Nr is not particularly limited, and is, for example, 1.47 or more, and preferably 1.51 or more. On the other hand, the value of the refractive index Nr is, for example, 1.65 or less, and preferably 1.57 or less. Specifically, the value of the refractive index Nr is 1.47 or more and 1.65 or less, and preferably 1.51 or more and 1.57 or less. This is because it is easy to obtain a refractive index difference with the light-transmitting portion described later.

[0051] The difference Nt-Nr between the refractive index Nt of the light-transmitting portion 3 and the refractive index Nr of the light-absorbing portion 4 is not particularly limited, but is preferably 0.05 or less, and more preferably 0.03 or less. The refractive index difference Nt-Nr is, for example, 0 or more. By reducing the refractive index difference, total reflection can be appropriately suppressed and the viewing angle in the first direction (the left-right direction when used as an optical sheet for a display device placed in front of the passenger seat in a car) can be controlled.

[0052] 4 shows the angle θ that the interface between the light transmitting portion 3 and the light absorbing portion 4 makes with respect to the normal to the layer surface of the optical function layer 2. 11 , θ 12 The angle θ 11 is the angle between an interface 4a, which is on the right side of the light absorbing portion 4 when the optical sheet 10 is placed with the base layer 1 side facing the viewer, and the normal to the layer surface of the optical function layer 2. 12 is the angle between the interface 4b on the left side of the light absorbing portion 4 and the normal to the layer surface of the optical function layer 2 in the same posture.

[0053] Angle θ 11 and angle θ 12 (i.e., the inclination angle of the legs in the trapezoidal cross section) is not particularly limited, but is, for example, 4.0° or more, and preferably 4.5° or more. 11 and θ 12 When the angle θ is in the above range, it becomes easy to control the viewing angle in the first direction (the left-right direction when used as an optical sheet for a display device placed in front of the passenger seat of a car). 11 and angle θ 12 is, for example, 6.5° or less, and preferably 5.5° or less. 11 and angle θ 12 is, for example, 4.0° or more and 6.5° or less, and preferably 4.5° or more and 5.5° or less.

[0054] In this embodiment, the light incident side aperture ratio is, for example, 40% or less, preferably 35% or less. When the light incident side aperture ratio is within the above range, it becomes easy to control the viewing angle in the first direction (the left-right direction when used as an optical sheet for a display device disposed in front of the passenger seat of a vehicle). On the other hand, the light incident side aperture ratio is, for example, 25% or more, preferably 30% or more. When the light incident side aperture ratio is within the above range, it is possible to suppress a decrease in the luminance of the display device. That is, the light incident side aperture ratio is, for example, 25% or more and 40% or less, preferably 30% or more and 35% or less. As shown in FIG. 4, the above light incident side aperture ratio is the ratio (Wa / Pa) of the width Wa of the light transmission portion 3 existing between the light absorption portions 4 to the distance Pa between the centers of the adjacent light absorption portions 4 on the surface opposite to the substrate layer 1 side.

[0055] The height Da of the light absorption portion is not particularly limited, and is, for example, 110 μm or more, preferably 120 μm or more. When the height Da of the light absorption portion is within the above range, it becomes easy to control the viewing angle in the first direction (the left-right direction when used as an optical sheet for a display device disposed in front of the passenger seat of a vehicle). On the other hand, the height Da of the light absorption portion is equal to or less than the thickness of the optical functional layer, and is, for example, 140 μm or less.

[0056] The OD value (optical density value) of the light absorption portion is not particularly limited, and is, for example, 3.5 or more, preferably 4.0 or more. On the other hand, the OD value of the light absorption portion is, for example, 5.0 or less, preferably 4.5 or less. Specifically, the OD value of the light absorption portion is, for example, 3.5 or more and 5.0 or less, preferably 4.0 or more and 4.5 or less.

[0057] The method for measuring the OD value of the above light absorption portion is as follows. First, the composition constituting the light absorption portion is applied on an easily adherent PET film with a thickness of 60 μm, laminated with an untreated PET film, and one side thereof is UV-cured. Then, UV curing is also performed from the other side to produce a measurement sample. The transmittance of this light absorption layer is measured with a transmittance densitometer, and the OD value is calculated.

[0058] In FIGS. 1 to 4, an example is shown in which the interface between the light transmission part 3 and the light absorption part 4 is linear in the cross section. However, the present invention is not limited to this, and the interface may be a polygonal line, a convex curved surface, a concave curved surface, or the like. Further, in the plurality of light transmission parts 3 and light absorption parts 4, the cross-sectional shapes may be the same, or may have different cross-sectional shapes with a predetermined regularity.

[0059] 2. Substrate layer The substrate layer in the present embodiment is a flat sheet-like member that supports the optical functional layer. As the substrate layer, a resin substrate is used. As the material of the substrate layer, various materials can be used. For example, a material that is widely used as a material for an optical sheet incorporated in a display device and has excellent mechanical properties, optical properties, stability, processability, etc., and can be obtained at low cost can be used. Examples of such materials include polyesters such as polyethylene terephthalate (PET), triacetyl cellulose (TAC), acrylic resins, methacrylic resins, polycarbonates, and cycloolefin polymers.

[0060] As described later, when the optical sheet of the present embodiment is used in a liquid crystal display device, it is preferable that the birefringence (retardation) of the substrate layer is small in consideration of the combination of the surface light source device and the lower polarizing plate. As materials with small birefringence, TAC, methacrylic resin, and polycarbonate are preferably used. Further, in applications that require high heat resistance such as in-vehicle applications, polycarbonate with a high glass transition point is more preferable. Specifically, the glass transition point of polycarbonate is 143° C., which is suitable for in-vehicle applications that generally require durability at 105° C.

[0061] On the other hand, from the viewpoint of suppressing rainbow unevenness, it is also preferable that the birefringence (retardation) of the substrate layer is large. As a material with large birefringence, polyester is preferably used. Polyester is also advantageous in terms of cost and mechanical strength.

[0062] From the perspective of suppressing rainbow unevenness, the retardation of the base material layer is preferably 3000 nm or more. The upper limit of the retardation of the base material layer is not particularly limited, but is preferably about 30000 nm. If the retardation of the base material layer is too large, the base material layer may become considerably thick. From the perspective of thinning the base material layer, the retardation of the base material layer is more preferably 5000 nm or more and 25000 nm or less, and even more preferably 7000 nm or more and 20000 nm or less.

[0063] The retardation Re of the base material layer is represented by the following formula based on the refractive index nx in the direction with the largest refractive index (slow axis direction) in the plane of the base material layer, the refractive index ny in the direction perpendicular to the slow axis direction (fast axis direction), and the thickness d of the base material layer. Re = (nx - ny) × d

[0064] The above retardation is measured using a retardation measuring device. As the retardation measuring device, for example, the retardation measuring device "KOBRA-WR" manufactured by Oji Scientific Instruments Co., Ltd. is used. The measurement angle is 0° and the measurement wavelength is 589.3 nm.

[0065] The above nx - ny (hereinafter referred to as Δn) is preferably 0.05 or more. If the above Δn is too small, the thickness required to obtain the above retardation may become thick. On the other hand, the above Δn is preferably 0.25 or less. If the above Δn is too large, it is necessary to stretch the base material layer excessively, so the base material layer is likely to tear, break, etc., and the practicality as an industrial material may be significantly reduced. Therefore, the above Δn is more preferably 0.07 or more and 0.15 or less. Note that if the above Δn exceeds 0.15, the durability of the base material layer in the damp heat resistance test may be inferior. Since the durability in the damp heat resistance test is excellent, the above Δn is even more preferably 0.12 or less.

[0066] The nx is preferably 1.66 or more and 1.78 or less, and more preferably 1.68 or more and 1.73 or less. The ny is preferably 1.55 or more and 1.65 or less, and more preferably 1.57 or more and 1.62 or less. When the nx and ny are within the above ranges and the Δn relationship is satisfied, favorable antireflection performance and improved bright-area contrast can be achieved.

[0067] The polyester is not particularly limited as long as it satisfies the above-mentioned retardation. For example, a linear saturated polyester synthesized from an aromatic dibasic acid or its ester-forming derivative and a diol or its ester-forming derivative can be used. Specific examples include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly(1,4-cyclohexylene dimethylene terephthalate), and polyethylene-2,6-naphthalate. The polyester may also be a copolymer of these polyesters. A mixture of polyester and other resins containing polyester as the main component may also be used. In the above-mentioned mixture, the polyester content is, for example, 80 mol% or more. Among these, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferred due to their well-balanced mechanical and optical properties. Polyethylene terephthalate (PET) is particularly preferred. PET is versatile and readily available. Furthermore, PET has excellent transparency, thermal and mechanical properties, and its retardation can be controlled by stretching. Its intrinsic birefringence allows it to relatively easily achieve a large retardation even at a thin thickness.

[0068] When the base layer is a polyester base, the method for producing the polyester base is not particularly limited as long as it satisfies the above-mentioned retardation. For example, a method may be used in which the polyester is melted, extruded into a sheet, and the unstretched polyester is transversely stretched using a tenter or the like at a temperature above the glass transition temperature, followed by heat treatment. The transverse stretching temperature is preferably 80°C to 130°C, more preferably 90°C to 120°C. The transverse stretching ratio is preferably 2.5 to 6.0 times, more preferably 3.0 to 5.5 times. If the transverse stretching ratio is too high, the transparency of the resulting polyester base may be reduced. If the transverse stretching ratio is too low, the stretching tension will also be low, resulting in low birefringence of the resulting polyester base, which may not satisfy the above-mentioned retardation. In addition, in the method for producing a polyester base, the unstretched polyester may be transversely stretched under the above-mentioned conditions using a biaxial stretching tester, and then stretched in the machine direction relative to the transverse stretching (hereinafter also referred to as longitudinal stretching). In this case, the longitudinal stretching ratio is preferably 2 or less. If the longitudinal stretching ratio is too large, the Δn value may not satisfy the above-mentioned preferred range. The heat treatment temperature is preferably 100°C or higher and 250°C or lower, and more preferably 180°C or higher and 245°C or lower.

[0069] Methods for controlling the retardation of the polyester substrate prepared by the above-mentioned method within the above range include appropriately setting the stretching ratio, stretching temperature, and thickness of the polyester substrate to be prepared. Specifically, the higher the stretching ratio, the easier it is to obtain a high retardation, and the lower the stretching ratio, the easier it is to obtain a low retardation. The lower the stretching temperature, the easier it is to obtain a high retardation, and the higher the stretching temperature, the easier it is to obtain a low retardation. The thicker the thickness, the easier it is to obtain a high retardation, and the thinner the thickness, the easier it is to obtain a low retardation.

[0070] The thickness of the polyester base material is preferably 20 μm or more and 500 μm or less, more preferably 50 μm or more and 300 μm or less, and even more preferably 50 μm or more and 150 μm or less. If the thickness of the polyester base material is too thin, the retardation of the polyester base material may not satisfy the above range. Further, if the thickness of the polyester base material is too thin, the anisotropy of the mechanical properties becomes remarkable, and tearing, breaking, etc. are likely to occur, and the practicality as an industrial material may be significantly reduced. On the other hand, if the thickness of the polyester base material is too thick, the polyester base material is very rigid, the flexibility peculiar to the polymer film decreases, and the practicality as an industrial material may also decrease.

[0071] The total light transmittance of the base material layer is preferably 80% or more, more preferably 84% or more. The total light transmittance is measured in accordance with JIS K7361-1:1997.

[0072] 3. Other Layers The optical sheet in the present embodiment may have other layers other than the above base material layer and the above optical functional layer. Examples of other layers include a hard coat layer having a rough surface. Such a hard coat layer having a rough surface is, for example, a hard coating layer whose surface exhibits a rough surface with an arithmetic mean roughness Ra of 0.1 μm or more according to JIS B0601:1994. In the present embodiment, the arithmetic mean roughness Ra of the hard coat layer is preferably 0.2 μm or more, more preferably 0.4 μm or less. The hard coat layer can be made difficult to be damaged by contact with other adjacent optical members when the optical sheet is incorporated into the display device due to the rough surface on its surface. Further, the hard coat layer can suppress optical adhesion by the rough surface on its surface, and thus suppress the generation of interference fringes due to optical adhesion and make it difficult to deteriorate the optical performance. The hard coat layer having a rough surface may be disposed on the surface on the opposite side (light-emitting side) of the optical functional layer side of the base material layer, or may be disposed on the surface on the opposite side (light-incident side) of the base material layer side of the optical functional layer.

[0073] 4. Manufacturing Method The optical sheet in this embodiment can be manufactured, for example, as follows. First, a light transmission portion is formed on the base material layer. For this, a base material sheet serving as the base material layer is inserted between a mold roll having a shape on its surface that can transfer the shape of the light transmission portion and a nip roll arranged to face the mold roll. At this time, while supplying the composition constituting the light transmission portion between the base material sheet and the mold roll, the mold roll and the nip roll are rotated. As a result, the groove corresponding to the light transmission portion formed on the surface of the mold roll (a shape in which the shape of the light transmission portion is inverted) is filled with the composition constituting the light transmission portion, and the composition conforms to the surface shape of the mold roll.

[0074] Examples of the composition constituting the light transmission portion include ionizing radiation curable resins such as epoxy acrylate-based, urethane acrylate-based, polyether acrylate-based, polyester acrylate-based, and polythiol-based resins.

[0075] Light for curing is irradiated from the base material sheet side by a light irradiation device onto the composition constituting the light transmission portion sandwiched between the mold roll and the base material sheet and filled therein. Thereby, the composition can be cured and its shape can be fixed. Then, the base material layer and the formed light transmission portion are released from the mold roll by a release roll.

[0076] Next, a light absorption portion is formed. To form the light absorption portion, first, the composition constituting the light absorption portion is filled in the space between the above light transmission portions. Then, the excess of the above composition is scraped off with a doctor blade or the like. And the remaining composition is cured from the light transmission portion side to form the light absorption portion. Examples of the curing method include curing by ultraviolet irradiation and curing by heating.

[0077] The composition constituting the light absorption part is not particularly limited. For example, a composition in which colored light absorption particles are dispersed in a photocurable resin such as urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, and butadiene (meth) acrylate can be mentioned. In addition, a composition in which colored light absorption particles are dispersed in a thermosetting resin can also be used.

[0078] Further, instead of dispersing the light absorption particles, the entire light absorption part can also be colored with a pigment or a dye. As the light absorption particles, light-absorbing colored particles such as carbon black are preferably used. The light absorption particles are not limited to these, and colored particles that selectively absorb a specific wavelength according to the characteristics of the video light may be used. Specifically, carbon black, graphite, metal salts such as black iron oxide, organic fine particles colored with dyes or pigments, and glass beads can be mentioned. In particular, the colored organic fine particles are preferably used from the viewpoints of cost, quality, and ease of availability. The average particle diameter of the colored particles is preferably 1.0 μm or more and 20 μm or less, more preferably 1.0 μm or more and 10 μm or less, and even more preferably 1.0 μm or more and 4.0 μm or less. Here, the "average particle diameter" means the diameter obtained by observing 100 light absorption particles with an electron microscope, measuring their diameters, and calculating the arithmetic mean.

[0079] 5. Optical Sheet The optical sheet in the present embodiment has a rectangular shape having a pair of first sides L1 extending in the first direction and a pair of second sides L2 extending in the second direction in a plan view. The first side L1 may be longer, shorter, or the same as the second side L2. The first direction, the second direction, and the third direction are usually perpendicular to each other. In FIG. 1, the first side L1 is longer than the second side L2.

[0080] The use of the optical sheet of this embodiment is not particularly limited, and it can be used, for example, in a display device. In particular, the optical sheet of this embodiment is preferably used in an in-vehicle display device, and more preferably in a display device disposed in front of the passenger seat of the vehicle. The optical sheet may be disposed on the viewer's side of the display panel in the display device, or may be included in a surface light source device in the display device.

[0081] B-1. Surface light source device (first embodiment) The surface light source device of this embodiment includes the optical sheet of the first embodiment described above, and a light source that emits light incident on the optical sheet.

[0082] Surface light source devices are usually used in display devices. Fig. 5 is an exploded perspective view illustrating a display device including the surface light source device of this embodiment. Fig. 6 shows a portion of an exploded cross-sectional view of the display device taken along the line II-II in Fig. 5, and Fig. 7 shows a portion of an exploded cross-sectional view of the display device taken along the line III-III in Fig. 5. The display devices shown in Figs. 5 to 7 are examples of liquid crystal display devices.

[0083] As shown in Figures 5 to 7, a display device 50A equipped with a surface light source device 20 according to this embodiment includes a liquid crystal panel 15, the surface light source device 20, and a functional film 40. Although Figures 5 to 7 also show the orientation of the display device in an installed position, the installation position is not limited to this. For example, as shown in Figure 5, the display device is preferably disposed in a position in which the first direction D1 in Figures 1 to 4 is horizontal and the second direction D2 is vertical, but is not limited to this position. Each component will be described below.

[0084] The surface light source device 20 in FIGS. 5 to 7 has the above-described optical sheet 10A, is disposed on the side opposite to the observer side from the liquid crystal panel 15, and is an illumination device that emits planar light to the liquid crystal panel 15. Further, the surface light source device 20 in FIGS. 5 to 7 is configured as an edge light type surface light source device, and has a light guide plate 21, a light source 25, a light diffusion plate 26, a prism layer 27, a reflective polarizing plate 28, an optical sheet 10A, and a reflective sheet 29. As shown in FIGS. 5 to 7, in the surface light source device 20, the optical sheet 10A is disposed such that the base material layer 1 is on the observer side with respect to the optical functional layer 2.

[0085] As shown in FIGS. 5 to 7, the light guide plate 21 has a base portion 22 and a back surface optical element 23. The light guide plate 21 is a plate-like member formed of a light-transmissive material as a whole. As shown in FIGS. 5 to 7, one plate surface side on the observer side of the light guide plate 21 is a smooth surface, and the other plate surface side opposite thereto is a back surface, and a plurality of back surface optical elements 23 are arranged on the back surface.

[0086] As the materials for the base portion 22 and the back surface optical element 23, various materials can be used. For example, materials that are widely used as materials for optical sheets incorporated in display devices, have excellent mechanical properties, optical properties, stability, workability, etc., and are available at low cost can be used. Examples of such materials include thermoplastic resins such as polymer resins having an alicyclic structure, methacrylic resins, polycarbonates, polystyrenes, acrylonitrile-styrene copolymers, methyl methacrylate-styrene copolymers, ABS resins, and polyethersulfones, and epoxy acrylates and urethane acrylate-based reactive resins (such as ionizing radiation curable resins).

[0087] The base portion 22 is a plate shape having a predetermined thickness at a portion that guides light inside and serves as a base for the back surface optical element 23.

[0088] The back optical element 23 is a protruding element formed on the back side of the base 22, and is triangular prism-shaped in FIGS. 5 to 7. The back optical element 23 is columnar with the ridge line of the protruding top extending in the horizontal direction, and a plurality of back optical elements 23 are arranged at a predetermined pitch in a direction (vertical direction) orthogonal to the extending direction. The back optical elements 23 in FIGS. 5 to 7 have a triangular cross-section, but are not limited thereto, and may have any cross-sectional shape such as a polygon, a hemispherical shape, a part of a sphere, a lens shape, etc.

[0089] It is preferable that the arrangement direction of the plurality of back optical elements 23 is the light guiding direction. That is, they are arranged in a direction away from the light source 25, and the ridge lines of the respective back optical elements 23 extend parallel to the direction in which the light source 25 is arranged, or, in the case of a single long light source, the direction in which the light source extends.

[0090] Note that the "triangular shape" in this specification includes not only a strictly triangular shape but also a substantially triangular shape including limitations in manufacturing technology, errors during molding, etc. Similarly, terms used in this specification to specify other shapes and geometric conditions, such as terms like "parallel", "orthogonal", "ellipse", "circle", etc., are not restricted by a strict meaning and are to be interpreted including errors to the extent that similar optical functions can be expected.

[0091] The light guide plate 21 having such a configuration can be manufactured by extrusion molding or by shaping the back optical element 23 on the base 22. In the light guide plate 21 manufactured by extrusion molding, the base 22 and the back optical element 23 can be integrally formed. Also, when manufacturing the light guide plate 21 by shaping, the back optical element 23 may be made of the same resin material as the base 22 or a different material.

[0092] The light source 25 is disposed on one of the side surfaces (end surfaces) of the base 22 of the light guide plate 21 in the direction in which the rear optical elements 23 are arranged. The light source is not particularly limited and can be configured in various forms, such as a linear fluorescent lamp such as a cold cathode fluorescent tube, point-shaped LEDs (light-emitting diodes), or an incandescent lamp. In Figs. 5 to 7, the light source 25 is made up of a plurality of LEDs, and is configured so that the turning on and off of each LED and / or the brightness of each LED when lit can be individually and independently adjusted by a control device (not shown).

[0093] 5 to 7 show an example in which the light source 25 is disposed on one side surface (end surface) as described above, but a configuration in which a light source is disposed on the side surface (end surface) opposite to this side surface (end surface) may also be used. In this case, the shape of the rear surface optical element is also formed following a known example.

[0094] Next, the light diffusion plate 26 will be described. The light diffusion plate 26 is a member disposed on the light output side of the light guide plate 21 and has the function of diffusing and outputting light that has entered thereon. This further improves the uniformity of the light output from the light guide plate 21 and makes scratches on the light guide plate 21 less noticeable. Specific embodiments of the light diffusion plate include known light diffusion plates, such as a plate having a light diffusing agent dispersed in a base material. The light diffusion plate 26 can be used as a support plate for the prism layer 27, as shown in FIGS. 5 to 7. Furthermore, if the light output surface of the light guide plate 21 is smooth, the light diffusion plate 26 may be bonded to the light guide plate 21 to form an integrated structure.

[0095] As can be seen from Figures 5 to 7, the prism layer 27 is provided closer to the liquid crystal panel 15 than the light diffusion plate 26, and is a layer including unit prisms 27a that are convex toward the liquid crystal panel 15. In Figures 5 to 7, the unit prisms 27a have a predetermined cross section and extend in the light guide direction of the light guide plate 21 (the vertical direction in this embodiment). The multiple unit prisms 27a are arranged in a direction different from the light guide direction (the horizontal direction, orthogonal to the light guide direction in a plan view in this embodiment).

[0096] For the cross-sectional shape of the unit prism of such a prism layer, a known shape can be applied according to the required function. With such a shape, light can be further diffused or condensed.

[0097] In addition, the direction in which the unit prism extends and the direction in which it is arranged are not limited to the above form, and other forms may also be possible. For example, a form in which the unit prism has a predetermined cross-section and extends in a direction orthogonal to the light guiding direction of the light guide plate 21, and a plurality of unit prisms are arranged in the light guiding direction may be possible.

[0098] The reflective polarizing plate 28 has a function of decomposing incident light into two orthogonal polarization components (P wave and S wave), transmitting the polarization component in one direction (the direction parallel to the transmission axis) (for example, the P wave), and reflecting the polarization component in the other direction (the direction parallel to the reflection axis) orthogonal to the one direction (for example, the S wave). For the structure of such a reflective polarizing plate, a known one can be applied.

[0099] The reflection sheet 29 of the surface light source device 20 will be described. The reflection sheet 29 is a member for reflecting the light emitted from the back surface of the light guide plate 21 and making the light enter the light guide plate 21 again. As the reflection sheet 29, a sheet made of a material having a high reflectivity such as metal, or a sheet including a thin film made of a material having a high reflectivity (for example, a metal thin film) as a surface layer, that is, a so-called specular reflection-capable sheet can be preferably applied.

[0100] C-1. Display device (First Embodiment) The display device in the present embodiment includes the optical sheet of the first embodiment described above and a display panel. The display device is a device that displays an image composed of, for example, a moving image, a still image, character information, or a combination thereof on the display panel. According to the display device of the present embodiment, it is possible to control the emission of image light in the vertical and horizontal directions. In particular, in the case of a display device arranged in front of the passenger seat of a vehicle, it is possible to control the emission of image light to the driver side, and it is also possible to control the reflection of image light on the windshield in front of the passenger seat.

[0101] The display device of this embodiment has two further embodiments. The display device of this embodiment includes a surface light source device, and the surface light source device may include the above-mentioned optical sheet. In addition, in the display device of this embodiment, the above-mentioned optical sheet may be disposed on the viewer's side of the display panel.

[0102] C-1-1. Display device (first example of first embodiment) The display device of this embodiment includes a surface light source device including the optical sheet of the first embodiment described above, and a display panel laminated on the surface light source device.

[0103] 5 to 7 are schematic plan views and cross-sectional views showing an example of a display device according to this embodiment. Note that, as Fig. 5 to Fig. 7 have been described above in the section "B-1. Surface light source device (first embodiment)", their description will be omitted here.

[0104] 1. Surface light source device The surface light source device has been described above in the section "B-1. Surface light source device (first embodiment)," so a description thereof will be omitted here.

[0105] 2. Display panel The display panel is, for example, a liquid crystal panel. The liquid crystal panel 15 shown in Figures 5 to 7 has an upper polarizer 13 arranged on the viewer side, a lower polarizer 14 arranged on the surface light source device 20 side, and a liquid crystal layer 12 arranged between the upper polarizer 13 and the lower polarizer 14. The upper polarizer 13 and the lower polarizer 14 have the function of decomposing incident light into two orthogonal polarized components (P wave and S wave), transmitting the polarized component in one direction (parallel to the transmission axis) (for example, P wave) and absorbing the polarized component in the other direction (parallel to the absorption axis) orthogonal to the one direction (for example, S wave).

[0106] The liquid crystal layer 12 has a plurality of pixels arranged vertically and horizontally along the layer surface, and an electric field can be applied to each pixel. The orientation of the pixel changes when an electric field is applied. As a result, the polarization direction of a polarized component (e.g., P wave) parallel to the transmission axis that has passed through the lower polarizer 14 located on the surface light source device 20 side (i.e., the light incident side) is rotated by 90° when passing through a pixel to which an electric field is applied, while maintaining its polarization direction when passing through a pixel to which no electric field is applied. Therefore, depending on whether or not an electric field is applied to the pixel, it is possible to control whether the polarized component (e.g., P wave) that has passed through the lower polarizer 14 is further transmitted through the upper polarizer 13 located on the light output side, or whether it is absorbed and blocked by the upper polarizer 13.

[0107] In this way, the liquid crystal panel 15 has a structure that controls the transmission or blocking of light from the surface light source device 20 for each pixel to display an image.

[0108] There are several types of liquid crystal panels, but the type is not particularly limited and any known type of liquid crystal panel can be used, such as TN, STN, VA, MVA, IPS, and OCB.

[0109] 3. Other materials As shown in Figures 5 to 7, the display device of this embodiment may have a functional film 40 arranged on the light-emitting side of the liquid crystal panel 15. The functional film 40 is a member having the function of improving the quality of image light and protecting the display device 50A. Examples of the functional film include an anti-reflection film, an anti-glare film, a hard coat film, a color correction film, and a light diffusion film, and the functional film may be formed by using one of these films or a combination of two or more of them.

[0110] 4. Effect Next, the operation of the display device 50A having the above configuration will be described with reference to examples of optical paths. However, these optical path examples are conceptual examples for the purpose of explanation and do not strictly represent the degree of reflection or refraction.

[0111] First, as shown in FIG. 7, the light emitted from the light source 25 enters the light guide plate 21 from the light incident surface, which is the side surface (end surface) of the light guide plate 21. In FIG. 7, as an example, the optical paths of the light L21 and L22 incident on the light guide plate 21 from the light source 25 are shown.

[0112] As shown in FIG. 7, the light L21 and L22 incident on the light guide plate 21 repeatedly undergo total internal reflection due to the refractive index difference with air at the light emitting side surface and the back surface on the opposite side of the light guide plate 21, and proceed in the light guiding direction (the direction downward in the plane of FIG. 7).

[0113] However, the back surface optical element 23 is disposed on the back surface of the light guide plate 21. Therefore, as shown in FIG. 7, the light L21 and L22 traveling in the light guide plate 21 change their traveling directions by the back surface optical element 23 and may enter the light emitting surface and the back surface at an incident angle less than the total internal reflection critical angle. In this case, the light can be emitted from the light emitting surface and the back surface on the opposite side of the light guide plate 21.

[0114] The light L21 and L22 emitted from the light emitting surface head toward the light diffusion plate 26 disposed on the light emitting side of the light guide plate 21. On the other hand, the light emitted from the back surface is reflected by the reflection sheet 29 disposed on the back side of the light guide plate 21, enters the light guide plate 21 again, and travels in the light guide plate 21.

[0115] The light traveling in the light guide plate 21 and the light whose direction is changed by the back surface optical element 23 and reaches the light emitting surface at an incident angle less than the total internal reflection critical angle occur in each region along the light guiding direction in the light guide plate 21. Therefore, the light traveling in the light guide plate 21 gradually comes to be emitted from the light emitting surface. Thereby, the light quantity distribution along the light guiding direction of the light emitted from the light emitting surface of the light guide plate 21 can be made uniform.

[0116] The light emitted from the light guide plate 21 then reaches the light diffusion plate 26, and the uniformity is enhanced. Then, it is diffused or condensed as necessary by the prism layer 27, and the light emitted from the prism layer 27 reaches the reflective polarizing plate 28. Here, the light in the polarization direction along the transmission axis of the reflective polarizing plate 28 passes through the reflective polarizing plate 28 and heads toward the optical sheet 10A.

[0117] On the other hand, light polarized along the reflection axis of the reflective polarizer 28 is reflected as shown by the dotted arrow in FIG. 7 and returned to the light guide plate 21. The returned light is reflected by the light guide plate 21, the rear optical element 23, or the reflection sheet 29 and travels again toward the reflective polarizer 28. The polarization direction of some of the light changes during this reflection, and some of this light is transmitted through the reflective polarizer 28. The other light is returned again to the light guide plate. In this way, the light reflected by the reflective polarizer 28 can also be transmitted through the reflective polarizer 28 by repeated reflections. This increases the utilization efficiency of light from the light source 25. Here, the polarization direction of the light emitted from the reflective polarizer 28 is aligned with the transmission axis of the lower polarizer 14, and becomes polarized light that transmits through the lower polarizer 14.

[0118] The light that has exited the reflective polarizing plate 28 reaches the optical sheet 10 A. The light that has entered the optical sheet 10 A travels along the optical path described above.

[0119] Light emitted from the optical sheet 10A is incident on the lower polarizer 14 of the liquid crystal panel 15. The lower polarizer 14 transmits one polarized component of the incident light and absorbs the other polarized component. The light that passes through the lower polarizer 14 is selectively transmitted through the upper polarizer 13 depending on the state of the electric field applied to each pixel. In this way, the liquid crystal panel 15 selectively transmits light from the surface light source device 20 pixel by pixel, allowing a viewer of the liquid crystal display device to view an image. At this time, the image light is provided to the viewer via the functional film 40, improving the quality of the image.

[0120] 5.Applications The display device of this embodiment is preferably used in applications that require control of the emission of image light in the vertical and horizontal directions.

[0121] The display device of this embodiment is preferably used as an in-vehicle display device, for example, and particularly as a passenger seat display device disposed in front of the passenger seat of a vehicle.

[0122] As shown in FIGS. 5 to 7, in the display device 50A according to the present embodiment, the base material layer 1 in the optical sheet 10A is arranged on the observer side with respect to the optical function layer 2. FIG. 8(a) is a schematic view of the front inside of a vehicle in which the display device 50A according to the present embodiment is arranged in front of the passenger seat of the vehicle. FIG. 8(b) is a plan view for explaining the state of the optical sheet of the display device in FIG. 8(a). In FIGS. 8(a) and 8(b), the first direction D1 in the optical sheet is in the horizontal direction (the left-right direction of the vehicle), the second direction D2 is in the vertical direction, and the third direction D3 is in the horizontal direction (the front-rear direction of the vehicle). On the other hand, the installation posture of the display device is not limited to this.

[0123] When the display device according to the present embodiment is used as a display device for the passenger seat arranged in front of the passenger seat of the vehicle, it is possible to control the emission of video light to the driver side. Further, it is possible to control the reflection of video light on the windshield in front of the passenger seat, and it is possible to suppress the driver from visually recognizing the reflection on the windshield.

[0124] Further, the display device according to the present embodiment can be used as a display device for the rear seat arranged on the ceiling or headrest of the vehicle. When display devices for the rear seats are installed in the rear seats respectively, it is possible to suppress the emission of video light in the left-right direction and suppress the reduction in visibility caused by the reflection of the video light of the display device for the rear seat adjacent to the observer's display device for the rear seat. In particular, when the observer is observing a low-luminance image on the display device for the rear seat and a high-luminance image is being displayed on the adjacent display device for the rear seat, the reduction in visibility can be further suppressed. Further, it is possible to suppress the emission of video light in the upward direction, and in particular, control the reflection of video light on the ceiling of the rear seat at night, and suppress the driver from visually recognizing the reflection on the ceiling.

[0125] In addition, the display device in the present embodiment can be used for display devices arranged in seats of buses, trains, airplanes, etc. In this case, the emission of video light in the left - right direction can be suppressed, protecting privacy. Also, the emission of video light in the upward direction can be suppressed, especially controlling the reflection of video light on the ceiling of the seat at night, and suppressing the visual recognition of the reflection on the ceiling by people other than the observer.

[0126] The display device in the present embodiment can also be used for various applications such as advertising, presentation, television video, and display of various information indoors or outdoors.

[0127] C - 1 - 2. Display Device (Second Example of the First Embodiment) The display device in the present embodiment includes a display panel and the optical sheet of the above - described first embodiment arranged on the observer side of the display panel.

[0128] FIG. 9 is an exploded cross - sectional view illustrating the display device in the present embodiment. As shown in FIG. 9, the display device 50E in the present embodiment includes a display panel 30 and an optical sheet 10A arranged on the observer side of the display panel 30. As shown in FIG. 9, in the display device 50E, the optical sheet 10A is arranged such that the base material layer 1 is on the observer side with respect to the optical functional layer 2. FIG. 9 also shows the orientation of the display device in the installed posture, but the installed posture is not limited to this. For example, as shown in FIG. 9, the display device is preferably arranged in a posture such that the first direction D1 in FIGS. 1 - 4 is the horizontal direction and the second direction D2 is the vertical direction, but is not limited to this posture.

[0129] 1. Optical Sheet Since the optical sheet is described in the section of "A - 1. Optical Sheet (First Embodiment)", the description here is omitted.

[0130] 2. Display Panel Examples of the display panel include a liquid crystal panel and an organic electroluminescence panel. The liquid crystal panel is the same as the liquid crystal panel described in the above section "C-1-1. Display Device (First Example of First Embodiment)". The organic electroluminescence panel may be a known organic electroluminescence panel.

[0131] 3. Other materials The display device of this embodiment may have a functional film 40 arranged on the light-emitting side of the optical sheet 10A, as shown in Fig. 9. The functional film is the same as the functional film described in the above section "C-1-1. Display device (first example of first embodiment)".

[0132] When the display panel is a liquid crystal panel, the display device of this embodiment usually has a surface light source device on the surface of the liquid crystal panel opposite to the optical sheet side. The surface light source device can be a known surface light source device.

[0133] On the other hand, when the display panel is an organic electroluminescence panel, the organic electroluminescence panel is of a self-luminous type.

[0134] 4.Applications The use of the display device in this embodiment is similar to the use described in the above section "C-1-1. Display device (first example of first embodiment)," and therefore a description thereof will be omitted here.

[0135] A-2. Optical sheet (second embodiment) As shown in FIGS. 1 to 4, for example, the optical sheet 10B of this embodiment includes a base material layer 1 and an optical functional layer 2 laminated on one surface of the base material layer 1. The optical sheet 10B of this embodiment has a rectangular shape having a pair of first sides L1 extending in the first direction and a pair of second sides L2 extending in the second direction in a plan view. The optical functional layer 2 has a plurality of light transmission portions 3 having a predetermined cross section and extending in one direction, and light absorption portions 4 formed between adjacent light transmission portions 3. A predetermined cross section of the light transmission portion 3 is trapezoidal, and the short upper base is on the light incident side. The optical sheet 10B is an optical sheet for a display device disposed in front of the passenger seat of a vehicle, and the extending direction of the light transmission portion 3 has an angle of 1.5° or more and 20° or less with respect to the second direction D2.

[0136] Details of FIGS. 1 to 4 are described in the section of the above "A-1. Optical Sheet (First Embodiment)", and thus the description here is omitted.

[0137] The optical sheet in this embodiment includes an optical functional layer having a light transmission portion and a light absorption portion that extend in a predetermined direction and have a predetermined cross section, thereby reducing the transmittance of light in a direction inclined by ±30° toward the first direction with respect to the third direction. Specifically, when the transmittance of light in the third direction is 100%, the relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±30° toward the first direction with respect to the third direction, can be 1% or less.

[0138] Furthermore, in a state where the light emission angle in the first direction D1 is controlled, since the extending direction of the light transmission portion 3 has an angle θ of 1.5° or more and 20° or less with respect to the second direction, the light emission angle in the second direction D2 can be controlled.

[0139] Therefore, when the optical sheet of this embodiment is used for a display device, the light emission angles of the display device in the left-right direction and the up-down direction can be controlled. More specifically, when used as an optical sheet for a display device disposed in front of the passenger seat of a vehicle, it is possible to control the emission of video light toward the driver's side, and it is also possible to control the reflection of video light on the front glass in front of the passenger seat.

[0140] The optical sheet in this embodiment is an optical sheet for a display device disposed in front of the passenger seat of a vehicle.

[0141] Other features of the optical sheet in this embodiment are the same as those of the "A-1. Optical Sheet (First Embodiment)" described above, and thus the description here is omitted.

[0142] B-2. Surface Light Source Device (Second Embodiment) The surface light source device 20 of this embodiment includes, for example, as shown in FIGS. 5 to 7, the optical sheet 10B of the second embodiment described above, and a light source 25 that emits light incident on the optical sheet 10B. The surface light source device of this embodiment is used for a display device for the passenger seat.

[0143] Details of FIGS. 5 to 7 are described in the section of the above "B-1. Surface Light Source Device (First Embodiment)", and thus the description here is omitted.

[0144] Regarding other members of the light source and the surface light source device, they are described in the section of the above "B-1. Surface Light Source Device (First Embodiment)", and thus the description here is omitted.

[0145] C-2. Display Device (Second Embodiment) The display device in this embodiment includes the optical sheet of the second embodiment described above and a display panel. According to the display device of this embodiment, when used as a display device disposed in front of the passenger seat of a vehicle, it is possible to control the emission of video light to the driver side, and it is also possible to control the reflection of video light on the windshield in front of the passenger seat.

[0146] The display device in this embodiment further has two embodiments. The display device of this embodiment includes a surface light source device, and the surface light source device may include the above-described optical sheet. Also, in the display device of this embodiment, the above-described optical sheet may be disposed on the observer side of the display panel.

[0147] C-2-1. Display Device (First Example of the Second Embodiment) The display device in this embodiment includes a surface light source device including the above-described optical sheet, and a display panel laminated on the surface light source device.

[0148] Figs. 5 to 7 are schematic plan views and cross-sectional views showing an example of the display device of this embodiment. Since Figs. 5 to 7 are described in the section of "B-1. Surface light source device (first embodiment)", the description here is omitted. As shown in Figs. 5 to 7, in the display device 50B in this embodiment, the base material layer 1 in the optical sheet 10B is arranged so as to be on the observer (passenger seat) side with respect to the optical functional layer 2.

[0149] 1. Surface light source device Since the surface light source device is described in the section of "B-2. Surface light source device (second embodiment)", the description here is omitted.

[0150] 2. Display panel and other members Since the display panel and other members are described in the section of "C-1-1. Display device (first example of the first embodiment)", the description here is omitted.

[0151] 3. Applications The display device in this embodiment is used as a display device arranged in front of the passenger seat of a vehicle. Fig. 8(a) is a schematic view of the front inside of a vehicle in which the display device 50B in this embodiment is arranged in front of the passenger seat. Fig. 8(b) is a plan view for explaining the state of the optical sheet of the display device 50B in Fig. 8(a). In Figs. 8(a) and 8(b), the first direction D1 in the optical sheet is arranged to be the horizontal direction (left-right direction of the vehicle), the second direction D2 is arranged to be the vertical direction, and the third direction D3 is arranged to be the horizontal direction (front-rear direction of the vehicle). On the other hand, the installation posture of the display device is not limited to this.

[0152] C-2-2. Display device (second example of the second embodiment) The display device in this embodiment includes a display panel, and the optical sheet of the above-described second embodiment arranged on the observer side of the display panel.

[0153] FIG. 9 is an exploded cross-sectional view illustrating the display device 50F in the present embodiment. Since FIG. 9 has been described in the section of "C-1-2. Display device (second example of the first embodiment)", the description here is omitted. As shown in FIG. 9, in the display device 50F in the present embodiment, the base material layer 1 in the optical sheet 10B is arranged so as to be on the observer (passenger seat) side with respect to the optical functional layer 2.

[0154] 1. Optical sheet Since the optical sheet has been described in the section of "A-2. Optical sheet (second embodiment)", the description here is omitted.

[0155] 2. Display panel and other members Since the display panel and other members have been described in the section of "C-1-2. Display device (second example of the first embodiment)", the description here is omitted.

[0156] 4. Use The display device in the present embodiment is used as a display device arranged in front of the passenger seat of a vehicle. Since the use of the display device in the present embodiment is the same as the use described in the section of "C-1-2. Display device (second example of the first embodiment)", the description here is omitted.

[0157] C-3. Display device (third embodiment) The display device of the present embodiment is a display device including an optical sheet and a display panel, the optical sheet includes a base material layer and an optical functional layer laminated on one surface of the base material layer, the optical functional layer has a plurality of light transmission portions having a predetermined cross-section and extending in one direction, and a light absorption portion formed between adjacent light transmission portions, the predetermined cross-section of the light transmission portion is trapezoidal, the short upper base is the light incident side, the optical sheet has a relative transmittance which is a ratio of the light transmittance in a direction inclined by ±30° from the normal direction to the left and right directions to be 1% or less when the light transmittance in the normal direction of the main surface of the optical sheet is 100% when the display device is installed, and the extending direction of the light transmission portion viewed from the normal direction has an angle of 1.5° or more and 20° or less with respect to the vertical direction.

[0158] The display device in this embodiment has two further embodiments. The display device of this embodiment includes a surface light source device, and the surface light source device may include the above-described optical sheet. Also, in the display device of this embodiment, the above-described optical sheet may be disposed on the observer side of the display panel.

[0159] C-3-1. Display Device (First Example of the Third Embodiment) FIGS. 5 to 7 are schematic plan views and cross-sectional views showing an example of the display device of this embodiment. Also, FIGS. 1 to 4 are schematic perspective views, cross-sectional views, and plan views showing an example of the optical sheet in the display device of this embodiment. The display device 50C of this embodiment includes, as shown in FIGS. 5 to 7, a surface light source device 20 including an optical sheet 10C, and a liquid crystal panel 15 laminated on the surface light source device 20. The optical sheet 10C in this embodiment includes, as shown in FIGS. 1 to 4, a base material layer 1 and an optical functional layer 2 laminated on one surface of the base material layer 1. The optical functional layer 2 has a plurality of light transmission portions 3 having a predetermined cross-section and extending in one direction, and a light absorption portion 4 formed between adjacent light transmission portions 3. A predetermined cross-section of the light transmission portion 3 is trapezoidal, and the short upper base is on the light incident side. As shown in FIG. 2, when the transmittance of light in the normal direction N (the third direction D3 in FIGS. 1 to 4) of the main surface S of the optical sheet is 100% when the display device 50C is installed, the optical sheet 10C has a relative transmittance that is 1% or less in a direction inclined ±30° in the left-right direction from the normal direction N. Also, as shown in FIG. 3, when the display device 50C is installed, the optical sheet 10C has an angle of 1.5° or more and 20° or less with respect to the vertical direction in the extending direction of the light transmission portion 3 viewed from the normal direction N.

[0160] Details of FIGS. 1 to 4 are described in the section of the above "A-1. Optical Sheet (First Embodiment)", so the description here is omitted. Also, FIGS. 5 to 7 are described in the section of the above "B-1. Surface Light Source Device (First Embodiment)", so the description here is omitted.

[0161] The display device 50C of the present embodiment has a predetermined optical sheet 10C. The optical sheet 10C in the present embodiment has a relative transmittance, which is the ratio of the light transmittance in the direction inclined by ±30° in the left - right direction with respect to the normal direction, of a value equal to or less than a predetermined value when the display device is installed. Thus, it is possible to control the light emission angle of the display device in the left - right direction. Further, in a state where the light emission angle in the left - right direction is controlled, since the extending direction of the light transmission portion as viewed from the normal direction has an angle θ within a predetermined range with respect to the vertical direction, it is possible to control the light emission angle of the display device in the up - down direction.

[0162] Therefore, it becomes a display device capable of controlling the light emission angles in the left - right direction and the up - down direction. More specifically, when arranged in front of the passenger seat of a vehicle, it is possible to control the emission of video light toward the driver's side and to control the reflection of video light on the windshield in front of the passenger seat.

[0163] 1. Surface light source device The surface light source device includes a predetermined optical sheet. As shown in FIGS. 1 - 4, the optical sheet 10C in the present embodiment has a relative transmittance, which is the ratio of the light transmittance in the direction inclined by ±30° in the left - right direction from the normal direction N (the third direction D3 in FIGS. 1 - 4) of the main surface of the optical sheet, of 1% or less when the light transmittance in the normal direction of the optical sheet is set to 100%. The relative transmittance of the above - mentioned light is preferably 0.6% or less, and more preferably 0.4% or less.

[0164] In the optical sheet of the present embodiment, when the light transmittance in the normal direction is set to 100%, the relative transmittance, which is the ratio of the light transmittance in the direction inclined by ±20° in the left - right direction with respect to the normal direction, is preferably 10% or less, and more preferably 5% or less.

[0165] Furthermore, in the optical sheet of this embodiment, when a display device is installed, the extension direction of the light-transmitting portion, as viewed from the normal direction, forms an angle of 1.5° or more and 20° or less with respect to the vertical direction. The angle θ is 1.5° or more, and may be 5° or more, or 10° or more. On the other hand, the angle θ is 20° or less and may be 15° or less. When the angle θ is within the above range, it is possible to control the light output angle in the left-right direction. Note that in FIGS. 1 and 3, the light-transmitting portion 3 has an angle θ on the right side (+D1 side) with respect to the vertical direction. In this case, it is preferable that the left side (-D1 side) is the driver's seat side. On the other hand, the light-transmitting portion 3 may have an angle θ on the left side (-D1 side) with respect to the second direction D2. In this case, it is preferable that the right side (+D1 side) is the driver's seat side.

[0166] The angle θ is calculated using the following method. First, the display device 50 is set up as shown in FIGS. 8(a) and 8(b). The optical sheet of the display device 50 may be vertically or horizontally oriented. Next, when viewed from the normal direction of the main surface of the optical sheet (the third direction D3 in FIG. 8(b)), i.e., when viewed from the front by an observer (e.g., a passenger seat), the smaller of the angles formed between the vertical line (a line in the direction of gravity) and the boundary line BL between the light-transmitting portion 3 and the light-absorbing portion 4 is measured. When measuring the angle, the boundary line BL between the light-transmitting portion 3 and the light-absorbing portion 4 on the surface of the short upper base of the light-transmitting portion 3 and the long lower base of the light-absorbing portion 4 of the optical function layer 2 is used. Furthermore, as shown in FIG. 8(b), the angle is measured at two locations on each of the left and right sides of the display device 50, and the arithmetic average of the four measured values is defined as the angle θ. The two locations are 1 / 3 of the vertical length K of the display device 50 from the top of the display device 50, and 1 / 3 of the vertical length K of the display device 50 from the bottom of the display device 50.

[0167] In this embodiment, the features of the optical sheet having the above optical characteristics and other features are the same as those of the above-described "A-1. Optical Sheet (First Embodiment)", so the description here is omitted. As for the other members of the surface light source device, since they are described in the section of the above "B-1. Surface Light Source Device (First Embodiment)", the description here is omitted.

[0168] 2. Display Panel and Other Members The display panel and other members are described in the section of the above "C-1-1. Display Device (First Example of the First Embodiment)", so the description here is omitted.

[0169] 3. Applications The applications of the display device in this embodiment are the same as those of the above-described "C-1-1. Display Device (First Example of the First Embodiment)", so the description here is omitted.

[0170] C-3-2. Display Device (Second Example of the Third Embodiment) FIG. 9 is a schematic plan view and a cross-sectional view showing an example of the display device of the present embodiment. FIGS. 1 to 4 are schematic perspective views, cross-sectional views, and plan views showing an example of the optical sheet in the display device of the present embodiment. As shown in FIG. 9, the display device 50G of the present embodiment includes a display panel 30 and an optical sheet 10C disposed on the observer side of the display panel 30. As shown in FIGS. 1 to 4, the optical sheet 10C in the present embodiment includes a base material layer 1 and an optical functional layer 2 laminated on one surface of the base material layer 1. The optical functional layer 2 has a plurality of light transmission portions 3 having a predetermined cross-section and extending in one direction, and a light absorption portion 4 formed between adjacent light transmission portions 3. The predetermined cross-section of the light transmission portion 3 is trapezoidal, and the short upper base is the light incident side. As shown in FIG. 2, when the display device 50G is installed, the optical sheet 10C has a relative transmittance that is the ratio of the light transmittance in the direction inclined by ±30° in the left-right direction from the normal direction N (the third direction D3 in FIGS. 1 to 4) of the main surface S of the optical sheet to 100% of 1% or less. Further, as shown in FIG. 3, when the display device 50G is installed, the extending direction of the light transmission portion 3 viewed from the normal direction N of the optical sheet 10C has an angle of 1.5° or more and 20° or less with respect to the vertical direction.

[0171] Details of FIGS. 1 to 4 are described in the section of "A-1. Optical Sheet (First Embodiment)" above, so the description here is omitted. Also, since FIG. 9 is described in the section of "C-1-2. Display Device (Second Example of First Embodiment)" above, the description here is omitted.

[0172] 1. Optical Sheet The optical sheet is the same as the optical sheet described in the section of "C-3-1. Display Device (First Example of Third Embodiment)" above, so the description here is omitted.

[0173] 2. Display Panel and Other Members The display panel and other members are described in the section of "C-1-2. Display Device (Second Example of First Embodiment)" above, so the description here is omitted.

[0174] 3. Use The use of the display device in this embodiment is similar to that of the above-mentioned "C-1-1. Display device (first example of first embodiment)", and therefore a description thereof will be omitted here.

[0175] C-4. Display device (fourth embodiment) The display device of this embodiment comprises an optical sheet and a display panel, and is disposed in front of the passenger seat of a vehicle. The optical sheet comprises a base layer and an optical functional layer laminated on one side of the base layer. The optical functional layer has a plurality of light-transmitting portions having a predetermined cross-section and extending in one direction, and light-absorbing portions formed between adjacent light-transmitting portions. The predetermined cross-section of the light-transmitting portions is trapezoidal, with the shorter upper base being the light-incident side. When the display device is disposed in front of the passenger seat of a vehicle, the extension direction of the light-transmitting portions, as viewed from the normal direction of the main surface of the optical sheet, forms an angle of 1.5° or more and 20° or less with respect to the vertical direction.

[0176] The display device of this embodiment has two further embodiments. The display device of this embodiment includes a surface light source device, and the surface light source device may include the above-mentioned optical sheet. In addition, in the display device of this embodiment, the above-mentioned optical sheet may be disposed on the viewer's side of the display panel.

[0177] C-4-1. Display device (first example of the fourth embodiment) Figs. 5 to 7 are schematic plan views and cross-sectional views showing an example of the display device of the present embodiment. Figs. 1 to 4 are schematic perspective views, cross-sectional views, and plan views showing an example of the optical sheet in the display device of the present embodiment. The display device 50D in the present embodiment includes, as shown in Figs. 5 to 7, a surface light source device 20 including an optical sheet 10D, and a liquid crystal panel 15 laminated on the surface light source device 20, and is a display device arranged in front of the passenger seat of a vehicle. The optical sheet 10D in the present embodiment includes, as shown in Figs. 1 to 4, a base material layer 1 and an optical functional layer 2 laminated on one surface of the base material layer 1. The optical functional layer 2 has a plurality of light transmission portions 3 having a predetermined cross-section and extending in one direction, and light absorption portions 4 formed between adjacent light transmission portions 3. A predetermined cross-section of the light transmission portion 3 is trapezoidal, and the short upper base is on the light incident side. When the display device is installed in front of the passenger seat of the vehicle, the optical sheet 10D has an extending direction of the light transmission portion 3 viewed from the normal direction N (the third direction D3 in Figs. 1 to 4) of the main surface of the optical sheet 10D at an angle of 1.5° or more and 20° or less with respect to the vertical direction.

[0178] The display device 50D in the present embodiment has a predetermined optical sheet 10D. The optical sheet 10D in the present embodiment includes an optical functional layer having light transmission portions and light absorption portions that extend in a predetermined direction and have a predetermined cross-section. When the display device is installed in front of the passenger seat of the vehicle, the transmittance of light in a direction inclined by ±30° in the left-right direction with respect to the normal direction can be reduced. Specifically, when the transmittance of light in the normal direction is 100%, the relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±30° in the left-right direction with respect to the normal direction, can be made 1% or less. Therefore, it is possible to control the light emission angle in the left-right direction of the display device.

[0179] Furthermore, in a state where the light emission angle in the left - right direction is controlled, the extending direction of the light transmission portion as viewed from the normal direction has an angle θ within a predetermined range with respect to the vertical direction, whereby the light emission angle in the up - down direction of the display device can be controlled. Therefore, the display device of the present embodiment can control the emission of video light toward the driver's side and can also control the reflection of video light on the windshield in front of the passenger seat.

[0180] 1. Surface light source device The surface light source device includes a predetermined optical sheet. The optical sheet 10D in the present embodiment includes an optical functional layer having a light transmission portion and a light absorption portion that extend in a predetermined direction and have a predetermined cross - section. Thereby, when a display device 50D having the predetermined optical sheet 10D is installed in front of the passenger seat of a vehicle, when the light transmittance in the normal direction N (the third direction D3 in FIGS. 1 to 4) of the main surface of the optical sheet 10D is set to 100%, the relative transmittance, which is the ratio of the light transmittance in the direction inclined ± 30° from the normal direction N to the left - right direction, can be made 1% or less. The relative transmittance of the above - mentioned light is preferably 0.6% or less, and more preferably 0.4% or less.

[0181] In the optical sheet of the present embodiment, when the light transmittance in the normal direction is set to 100%, the relative transmittance, which is the ratio of the light transmittance in the direction inclined ± 20° from the normal direction to the left - right direction, is preferably 10% or less, and more preferably 5% or less.

[0182] Furthermore, in the optical sheet of this embodiment, when a display device is installed in front of the passenger seat of a vehicle, the extension direction of the light-transmitting portion, as viewed from the normal direction, forms an angle of 1.5° or more and 20° or less with respect to the vertical direction. The angle θ is 1.5° or more, and may be 5° or more, or 10° or more. On the other hand, the angle θ may be 20° or less and 15° or less. When the angle θ is within the above range, it is possible to control the light output angle in the left-right direction. Note that in FIGS. 1 and 3, the light-transmitting portion 3 has an angle θ on the right side (+D1 side) with respect to the vertical direction. In this case, it is preferable that the left side (-D1 side) is the driver's seat side. On the other hand, the light-transmitting portion 3 may have an angle θ on the left side (-D1 side) with respect to the vertical direction. In this case, it is preferable that the right side (+D1 side) is the driver's seat side.

[0183] Other features of the optical sheet in this embodiment are the same as those in "A-1. Optical sheet (first embodiment)" above, and therefore will not be described here. Other members of the surface light source device have been described in "B-1. Surface light source device (first embodiment)" above, and therefore will not be described here.

[0184] 2. Display panels and other components The display panel and other members have been described above in the section "C-1-1. Display device (first example of first embodiment)," so a description thereof will be omitted here.

[0185] 3.Applications The display device in this embodiment is placed in front of the passenger seat of the vehicle. Fig. 8(a) is a schematic diagram of the front interior of the vehicle when a display device 50D in this embodiment is placed in front of the passenger seat of the vehicle. Fig. 8(b) is a plan view illustrating the state of the optical sheet of the display device in Fig. 8(a). In Figs. 8(a) and 8(b), the optical sheet is placed so that the left-right direction is horizontal (left-right direction of the vehicle), the up-down direction is vertical, and the thickness direction is horizontal (front-rear direction of the vehicle). However, the installation posture of the display device is not limited to this.

[0186] C-4-2. Display device (second example of the fourth embodiment) FIG. 9 is a schematic plan view and a cross-sectional view showing an example of the display device of the present embodiment. FIGS. 1 to 4 are schematic perspective views, cross-sectional views, and plan views showing an example of the optical sheet in the display device of the present embodiment. As shown in FIG. 9, the display device 50H in the present embodiment includes a display panel 30 and an optical sheet 10D disposed on the observer side of the display panel 30, and is a display device disposed in front of the passenger seat of the vehicle. As shown in FIGS. 1 to 4, the optical sheet 10D in the present embodiment includes a base material layer 1 and an optical functional layer 2 laminated on one surface of the base material layer 1. The optical functional layer 2 has a plurality of light transmission portions 3 having a predetermined cross-section and extending in one direction, and a light absorption portion 4 formed between adjacent light transmission portions 3. A predetermined cross-section of the light transmission portion 3 is trapezoidal, and the short upper base is on the light incident side. When the display device is installed in front of the passenger seat of the vehicle, the optical sheet 10D has an angle of 1.5° or more and 20° or less with respect to the vertical direction in the extending direction of the light transmission portion 3 viewed from the normal direction N of the main surface of the optical sheet 10D (the third direction D3 in FIGS. 1 to 4).

[0187] The display device 50D in the present embodiment has a predetermined optical sheet 10D. By including an optical functional layer having a light transmission portion and a light absorption portion that extend in a predetermined direction and have a predetermined cross-section, when the display device is installed in front of the passenger seat of the vehicle, the transmittance of light in a direction inclined by ±30° in the left-right direction with respect to the normal direction can be reduced. Specifically, when the transmittance of light in the normal direction is 100%, the relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±30° in the left-right direction with respect to the normal direction, can be made 1% or less. Therefore, it is possible to control the light emission angle in the left-right direction of the display device.

[0188] Furthermore, in a state where the light output angle in the left-right direction is controlled, the extension direction of the light-transmitting portion as viewed from the normal direction has an angle θ within a predetermined range with respect to the vertical direction, thereby making it possible to control the light output angle in the up-down direction of the display device. Therefore, the display device of this embodiment can control the output of image light toward the driver's side and can also control the reflection of image light on the windshield in front of the passenger seat.

[0189] 1. Optical sheets The optical sheet is the same as the optical sheet described above in the section "C-4-2. Display device (second example of the fourth embodiment)."

[0190] 2. Display panels and other components The display panel and other members have been described above in the section "C-1-1. Display device (first example of first embodiment)," so a description thereof will be omitted here.

[0191] 3.Applications The use of the display device in this embodiment is the same as that of "C-1-1. Display device (first example of first embodiment)" above.

[0192] A-3. Optical sheet (fifth embodiment) FIG. 1 is a schematic perspective view showing an example of the optical sheet of the present embodiment. Further, FIG. 10 shows a cross-sectional view of the optical sheet cut along the line indicated by I-I in FIG. 1. FIG. 3 is a plan view of the optical sheet shown in FIG. 1 as viewed along the direction (-D3 direction) from the base material layer 1 toward the optical functional layer 2. FIG. 4 is an enlarged cross-sectional view of the optical sheet shown in FIG. 10. As shown in FIGS. 1, 3, 4, and 10, the optical sheet 10E of the present embodiment includes a base material layer 1 and an optical functional layer 2 laminated on one surface of the base material layer 1. The optical sheet 10E of the present embodiment has a rectangular shape having a pair of first sides L1 extending in the first direction D1 and a pair of second sides L2 extending in the second direction D2 in a plan view. The optical functional layer 2 has a plurality of light transmission portions 3 having a predetermined cross-section and extending in one direction, and light absorption portions 4 formed between adjacent light transmission portions 3. As shown in FIG. 10, the cross-section of the light transmission portion 3 is trapezoidal, and the short upper base is the light incident side (light source side). In the present embodiment, as shown in FIG. 10, when the light transmittance in the third direction D3 is 100%, the relative transmittance, which is the ratio of the light transmittance in the direction inclined by ±20° toward the first direction D1 side with respect to the third direction D3, is 10% or less. Further, as shown in FIG. 3, the extending direction of the light transmission portion 3 has an angle θ of 1.5° or more and 20° or less with respect to the second direction D2.

[0193] According to the optical sheet 10A of the present embodiment, when the light transmittance in the third direction D3 is 100%, the relative transmittance, which is the ratio of the light transmittance in the direction inclined by ±20° toward the first direction side with respect to the third direction D3, is a predetermined value or less, so that it is possible to control the light emission angle in the first direction D1. Further, in a state where the light emission angle in the first direction D1 is controlled, since the extending direction of the light transmission portion 3 has an angle θ of 1.5° or more and 20° or less with respect to the second direction D2, it is possible to control the light emission angle in the second direction D2. This is because the viewing angle in the first direction D1 has a very narrow characteristic, and when an angle θ of 1.5° or more and 20° or less is provided while maintaining that state, the light transmittance in the second direction D2 rapidly decreases.

[0194] Therefore, when the optical sheet of the present embodiment is used in a display device, the light emission angles of the display device in the left - right direction and the up - down direction can be controlled. More specifically, when used as an optical sheet for a display device arranged in front of the passenger seat of a vehicle, it is possible to control the emission of video light toward the driver side and also possible to control the reflection of video light on the windshield.

[0195] Other features of the optical sheet in the present embodiment are the same as those of the "A - 1. Optical Sheet (First Embodiment)" described above, so the description here is omitted.

[0196] B - 3. Surface Light Source Device (Fifth Embodiment) The surface light source device 20 of the present embodiment includes, for example, as shown in FIGS. 5 to 7, the optical sheet 10E of the above - described fifth embodiment and a light source 25 that emits light incident on the optical sheet 10E.

[0197] Details of FIGS. 5 to 7 are described in the section of the above - mentioned "B - 1. Surface Light Source Device (First Embodiment)", so the description here is omitted.

[0198] Regarding the light source and other members of the surface light source device, they are described in the section of the above - mentioned "B - 1. Surface Light Source Device (First Embodiment)", so the description here is omitted.

[0199] C - 5. Display Device (Fifth Embodiment) The display device of the present embodiment includes the optical sheet of the above - described fifth embodiment and a display panel.

[0200] The display device in the present embodiment has two further embodiments. The display device of the present embodiment includes a surface light source device, and the surface light source device may include the above - described optical sheet. Also, in the display device of the present embodiment, the above - described optical sheet may be arranged on the observer side of the display panel.

[0201] C - 5 - 1. Display Device (First Example of the Fifth Embodiment) The display device of this embodiment includes a surface light source device including the optical sheet of the fifth embodiment described above, and a display panel laminated on the surface light source device.

[0202] 5 to 7 are schematic plan views and cross-sectional views showing an example of a display device 50I of this embodiment. As Fig. 5 to Fig. 7 have been described above in the section "B-1. Surface light source device (first embodiment)", a description thereof will be omitted here.

[0203] 1. Surface light source device The surface light source device has been described above in the section "B-3. Surface light source device (fifth embodiment)," so a description thereof will be omitted here.

[0204] 2. Display panels and other components The display panel and other members have been described above in the section "C-1-1. Display device (first example of first embodiment)," so a description thereof will be omitted here.

[0205] 3.Applications The use of the display device in this embodiment is similar to the use described in the above section "C-1-1. Display device (first example of first embodiment)," and therefore a description thereof will be omitted here.

[0206] C-5-2. Display Device (Second Example of Fifth Embodiment) The display device of this embodiment includes a display panel and the optical sheet of the fifth embodiment, which is arranged on the viewer side of the display panel.

[0207] 9A and 9B are a schematic plan view and a cross-sectional view showing an example of a display device 50J of this embodiment. Since FIG. 9 was described above in the section "C-1-2. Display device (second example of first embodiment)," a description thereof will be omitted here. As shown in FIG. 9A, the display device 50J of this embodiment is disposed such that the base layer 1 of the optical sheet 10I is on the observer (passenger seat) side relative to the optical function layer 2.

[0208] 1. Optical sheets Since the optical sheet is described in the section of "A-3. Optical Sheet (Fifth Embodiment)" above, the description here is omitted.

[0209] 2. Display Panel and Other Members Since the display panel and other members are described in the section of "C-1-2. Display Device (Second Example of First Embodiment)" above, the description here is omitted.

[0210] 3. Applications Since the applications of the display device in this embodiment are the same as those described in the section of "C-1-1. Display Device (First Example of First Embodiment)" above, the description here is omitted.

[0211] A-4. Optical Sheet (Sixth Embodiment) The optical sheet 10F of this embodiment includes, for example, as shown in FIGS. 1, 3, 4, and 10, a base material layer 1 and an optical functional layer 2 laminated on one surface of the base material layer 1. The optical sheet 10F of this embodiment has a rectangular shape having a pair of first sides L1 extending in the first direction and a pair of second sides L2 extending in the second direction in plan view. The optical functional layer 2 has a plurality of light transmission portions 3 having a predetermined cross section and extending in one direction, and light absorption portions 4 formed between adjacent light transmission portions 3. The predetermined cross section of the light transmission portion 3 is trapezoidal, with the short upper base on the light incident side. The optical sheet 10B is an optical sheet for a display device disposed in front of the passenger seat of a vehicle, and the extending direction of the light transmission portion 3 has an angle of 1.5° or more and 20° or less with respect to the second direction D2.

[0212] Regarding the details of FIGS. 1, 3, and 4, since they are described in the section of "A-1. Optical Sheet (First Embodiment)" above, the description here is omitted. Also, regarding FIG. 10, since it is described in the section of "A-3. Optical Sheet (Fifth Embodiment)" above, the description here is omitted.

[0213] The optical sheet in the present embodiment includes an optical functional layer having a light transmission portion and a light absorption portion that extend in a predetermined direction and have a predetermined cross-section, thereby reducing the transmittance of light in a direction inclined by ±20° toward the first direction with respect to the third direction. Specifically, when the transmittance of light in the third direction is 100%, the relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±20° toward the first direction with respect to the third direction, can be set to 10% or less.

[0214] Furthermore, in a state where the light emission angle in the first direction D1 is controlled, the extending direction of the light transmission portion 3 has an angle θ of 1.5° or more and 20° or less with respect to the second direction D2, thereby enabling control of the light emission angle in the second direction D2.

[0215] Therefore, when the optical sheet of the present embodiment is used in a display device, the light emission angles in the left-right direction and the up-down direction of the display device can be controlled. More specifically, when used as an optical sheet for a display device disposed in front of the passenger seat of a vehicle, it is possible to control the emission of video light toward the driver side and to control the reflection of video light on the windshield in front of the passenger seat.

[0216] The optical sheet in the present embodiment is an optical sheet for a display device disposed in front of the passenger seat of a vehicle.

[0217] Other features of the optical sheet in the present embodiment are the same as those of the above-described "A-1. Optical Sheet (First Embodiment)", and thus the description here is omitted.

[0218] B-4. Surface Light Source Device (Sixth Embodiment) The surface light source device 20 of the present embodiment includes, for example, as shown in FIGS. 5 to 7, the above-described optical sheet 10F of the sixth embodiment and a light source 25 that emits light incident on the optical sheet 10F. The surface light source device of the present embodiment is used for a display device for the passenger seat.

[0219] For details of FIGS. 5 to 7, since they are described in the section of "B-1. Surface Light Source Device (First Embodiment)" above, the description here is omitted.

[0220] Regarding the light source and other members of the surface light source device, since they are described in the section of "B-1. Surface Light Source Device (First Embodiment)" above, the description here is omitted.

[0221] C-6. Display Device (Sixth Embodiment) The display device of this embodiment includes the above-described optical sheet of the sixth embodiment and a display panel.

[0222] The display device in this embodiment further has two embodiments. The display device of this embodiment includes a surface light source device, and the surface light source device may include the above-described optical sheet. Also, in the display device of this embodiment, the above-described optical sheet may be disposed on the observer side of the display panel.

[0223] C-6-1. Display Device (First Example of Sixth Embodiment) The display device of this embodiment includes a surface light source device including the above-described optical sheet of the sixth embodiment and a display panel laminated on the surface light source device.

[0224] FIGS. 5 to 7 are schematic plan views and cross-sectional views showing an example of the display device 50K of this embodiment. For FIGS. 5 to 7, since they are described in the section of "B-1. Surface Light Source Device (First Embodiment)" above, the description here is omitted.

[0225] 1. Surface Light Source Device Since the surface light source device is described in the section of "B-4. Surface Light Source Device (Sixth Embodiment)" above, the description here is omitted.

[0226] 2. Display Panel and Other Members Since the display panel and other members are described in the section of "C-1-1. Display Device (First Example of First Embodiment)" above, the description here is omitted.

[0227] 3. Use Since the use of the display device in this embodiment is the same as that described in the section of "C-1-1. Display device (the first example of the first embodiment)", the description here is omitted.

[0228] C-6-2. Display device (the second example of the sixth embodiment) The display device of this embodiment includes a display panel and the optical sheet of the above-described sixth embodiment disposed on the observer side of the display panel.

[0229] FIG. 9 is a schematic plan view and a cross-sectional view showing an example of the display device 50L of this embodiment. Since FIG. 9 has been described in the section of "C-1-2. Display device (the second example of the first embodiment)", the description here is omitted.

[0230] 1. Optical sheet Since the optical sheet is the same as the optical sheet described in the section of "C-6-1. Display device (the first example of the sixth embodiment)", the description here is omitted.

[0231] 2. Display panel and other members Since the display panel and other members have been described in the section of "C-1-2. Display device (the second example of the first embodiment)", the description here is omitted.

[0232] 3. Use Since the use of the display device in this embodiment is the same as that described in the section of "C-1-1. Display device (the first example of the first embodiment)", the description here is omitted.

[0233] C-7. Display device (the seventh embodiment) The display device of this embodiment includes an optical sheet and a display panel. The optical sheet includes a base material layer and an optical functional layer laminated on one surface of the base material layer. The optical functional layer has a plurality of light transmission portions having a predetermined cross-section and extending in one direction, and light absorption portions formed between adjacent light transmission portions. The predetermined cross-section of the light transmission portion is trapezoidal, with the short upper base on the light incident side. When the transmittance of light in the normal direction of the main surface of the optical sheet is set to 100% when the display device is installed, the relative transmittance, which is the ratio of the transmittance of light in the direction inclined by ±20° from the normal direction to the left and right directions, is 10% or less. The extending direction of the light transmission portion as viewed from the normal direction has an angle of 1.5° or more and 20° or less with respect to the vertical direction.

[0234] The display device in this embodiment further has two other embodiments. The display device of this embodiment includes a surface light source device, and the surface light source device may include the above-described optical sheet. Also, in the display device of this embodiment, the above-described optical sheet may be disposed on the observer side of the display panel.

[0235] C-7-1. Display Device (First Example of the Seventh Embodiment) 5 to 7 are schematic plan views and cross-sectional views showing an example of a display device of this embodiment. Also, FIGS. 1, 3, 4, and 10 are schematic perspective views, cross-sectional views, and plan views showing an example of an optical sheet in the display device of this embodiment. As shown in FIGS. 5 to 7, a display device 50M of this embodiment includes a surface light source device 20 including an optical sheet 10G and a liquid crystal panel 15 laminated on the surface light source device 20. As shown in FIGS. 1, 3, 4, and 10, the optical sheet 10G of this embodiment includes a base layer 1 and an optical functional layer 2 laminated on one surface of the base layer 1. The optical functional layer 2 has a plurality of light-transmitting portions 3 having a predetermined cross section and extending in one direction, and light-absorbing portions 4 formed between adjacent light-transmitting portions 3. The predetermined cross section of the light-transmitting portion 3 is trapezoidal, with the shorter upper base facing the light-entering side. 10, when a display device 50M is installed, optical sheet 10G has a relative transmittance of 10% or less, which is the ratio of light transmittance in directions inclined by ±20° left and right from the normal direction N, when the light transmittance in the normal direction N (third direction D3 in FIGS. 1, 3, 4, and 10) of the main surface S of the optical sheet is taken as 100%. Also, as shown in FIG. 3, when a display device 50M is installed, optical sheet 10G has an extension direction of light transmitting portions 3 as viewed from the normal direction N that forms an angle of 1.5° or more and 20° or less with respect to the vertical direction.

[0236] Details of Figs. 1, 3, and 4 have been described above in the section "A-1. Optical sheet (first embodiment)," and therefore will not be described here. Fig. 10 has been described above in the section "A-3. Optical sheet (fifth embodiment)," and therefore will not be described here. Figs. 5 to 7 have been described above in the section "B-1. Surface light source device (first embodiment)," and therefore will not be described here.

[0237] The display device 50M of this embodiment includes a predetermined optical sheet 10G. When the display device is installed, the optical sheet 10G of this embodiment has a relative transmittance, which is the ratio of light transmittance in directions tilted ±20° left and right from the normal direction, that is equal to or less than a predetermined value, making it possible to control the light output angle of the display device in the left and right directions. Furthermore, when the light output angle in the left and right directions is controlled, the extension direction of the light-transmitting portion as viewed from the normal direction has an angle θ within a predetermined range with respect to the vertical direction, making it possible to control the light output angle of the display device in the up and down directions.

[0238] Therefore, the display device can control the light emission angle in the left-right and up-down directions. More specifically, when the display device is placed in front of the passenger seat of a car, it is possible to control the emission of image light toward the driver's side and also to control the reflection of the image light on the windshield in front of the passenger seat.

[0239] 1. Surface light source device The surface light source device includes a predetermined optical sheet. As shown in Figures 1, 3, 4, and 10, when a display device is installed, optical sheet 10G in this embodiment has a relative transmittance of 10% or less, which is the ratio of the light transmittance in directions tilted ±20° left and right from the normal direction N, when the light transmittance in the normal direction N (third direction D3 in Figures 1, 3, 4, and 10) of the main surface of the optical sheet is taken as 100%. The relative light transmittance is preferably 5% or less.

[0240] Furthermore, in the optical sheet of this embodiment, when a display device is installed, the extension direction of the light-transmitting portion as viewed from the normal direction forms an angle of 1.5° or more and 20° or less with respect to the vertical direction. The angle θ is 1.5° or more, and may be 5° or more, or 10° or more. On the other hand, the angle θ is 20° or less and may be 15° or less. When the angle θ is within the above range, it is possible to control the light output angle in the left-right direction. Note that in FIGS. 1 and 3, the light-transmitting portion 3 has an angle θ on the right side (+D1 side) with respect to the vertical direction. In this case, it is preferable that the left side (-D1 side) is the driver's seat side. On the other hand, the light-transmitting portion 3 may have an angle θ on the left side (-D1 side) with respect to the second direction D2. In this case, it is preferable that the right side (+D1 side) is the driver's seat side.

[0241] The characteristics of the optical sheet having the above optical properties and other characteristics in this embodiment are the same as those in the above-mentioned "A-1. Optical sheet (first embodiment)", so a description thereof will be omitted here. The other members of the surface light source device are described in the above-mentioned section "B-1. Surface light source device (first embodiment)", so a description thereof will be omitted here.

[0242] 2. Display panels and other components The display panel and other members have been described above in the section "C-1-1. Display device (first example of first embodiment)," so a description thereof will be omitted here.

[0243] 3.Applications The use of the display device in this embodiment is similar to that of the above-mentioned "C-1-1. Display device (first example of first embodiment)", and therefore a description thereof will be omitted here.

[0244] C-7-2. Display Device (Second Example of Seventh Embodiment) FIG. 9 is a schematic plan view and a cross-sectional view showing an example of the display device of the present embodiment. FIGS. 1, 3, 4, and 10 are schematic perspective views, cross-sectional views, and plan views showing an example of the optical sheet in the display device of the present embodiment. As shown in FIG. 9, the display device 50N of the present embodiment includes a display panel 30 and an optical sheet 10G disposed on the observer side of the display panel 30. As shown in FIGS. 1, 3, 4, and 10, the optical sheet 10G in the present embodiment includes a base material layer 1 and an optical functional layer 2 laminated on one surface of the base material layer 1. The optical functional layer 2 has a plurality of light transmission portions 3 having a predetermined cross-section and extending in one direction, and a light absorption portion 4 formed between adjacent light transmission portions 3. A predetermined cross-section of the light transmission portion 3 is trapezoidal, and the short upper base is the light incident side. As shown in FIG. 10, when the display device 50N is installed, the optical sheet 10G has a relative transmittance, which is the ratio of the light transmittance in the direction inclined by ±20° in the left-right direction from the normal direction N (the third direction D3 in FIGS. 1 to 4) of the main surface S of the optical sheet, of 10% or less when the light transmittance in the normal direction N is 100%. Further, as shown in FIG. 3, when the display device 50N is installed, the extending direction of the light transmission portion 3 viewed from the normal direction N of the optical sheet 10G has an angle of 1.5° or more and 20° or less with respect to the vertical direction.

[0245] Details of FIGS. 1, 3, and 4 are described in the section of "A-1. Optical Sheet (First Embodiment)" above, so the description here is omitted. Regarding FIG. 10, since it is described in the section of "A-3. Optical Sheet (Fifth Embodiment)" above, the description here is omitted. Regarding FIG. 9, since it is described in the section of "C-1-2. Display Device (Second Example of First Embodiment)" above, the description here is omitted.

[0246] 1. Optical Sheet The optical sheet is the same as the optical sheet described in the section of "C-7-1. Display Device (First Example of Seventh Embodiment)" above, so the description here is omitted.

[0247] 2. Display Panel and Other Members The display panel and other members have been described above in the section "C-1-2. Display device (second example of first embodiment)," so a description thereof will be omitted here.

[0248] 3.Applications The use of the display device in this embodiment is similar to that of the above-mentioned "C-1-1. Display device (first example of first embodiment)", and therefore a description thereof will be omitted here.

[0249] C-8. Display Device (Eighth Embodiment) The display device of this embodiment comprises an optical sheet and a display panel, and is disposed in front of the passenger seat of a vehicle. The optical sheet comprises a base layer and an optical functional layer laminated on one side of the base layer, the base layer being a resin base material. The optical functional layer has a plurality of light-transmitting portions having a predetermined cross-section and extending in one direction, and light-absorbing portions formed between adjacent light-transmitting portions. The predetermined cross-section of the light-transmitting portions is trapezoidal, with the shorter upper base being the light-incident side. When the display device is disposed in front of the passenger seat of a vehicle, the extension direction of the light-transmitting portions, as viewed from the normal direction of the main surface of the optical sheet, forms an angle of 1.5° or more and 20° or less with respect to the vertical direction.

[0250] The display device of this embodiment has two further embodiments. The display device of this embodiment includes a surface light source device, and the surface light source device may include the above-mentioned optical sheet. In addition, in the display device of this embodiment, the above-mentioned optical sheet may be disposed on the viewer's side of the display panel.

[0251] C-8-1. Display device (first example of eighth embodiment) Figs. 5 to 7 are schematic plan views and cross-sectional views showing an example of the display device of the present embodiment. Also, Figs. 1, 3, 4, and 10 are schematic perspective views, cross-sectional views, and plan views showing an example of the optical sheet in the display device of the present embodiment. The display device 50O in the present embodiment includes a surface light source device 20 including an optical sheet 10H and a liquid crystal panel 15 laminated on the surface light source device 20, and is a display device disposed in front of the passenger seat of a vehicle. The optical sheet 10H in the present embodiment includes a base material layer 1 and an optical functional layer 2 laminated on one surface of the base material layer 1, as shown in Figs. 1, 3, 4, and 10. The base material layer 1 is a resin base material, and the optical functional layer 2 has a plurality of light transmission portions 3 having a predetermined cross-section and extending in one direction, and a light absorption portion 4 formed between adjacent light transmission portions 3. A predetermined cross-section of the light transmission portion 3 is trapezoidal, and the short upper base is on the light incident side. When the display device is installed in front of the passenger seat of the vehicle, the optical sheet 10H has an extending direction of the light transmission portion 3 viewed from the normal direction N of the main surface of the optical sheet 10H (the third direction D3 in Figs. 1 to 4) with respect to the vertical direction. An angle of 1.5° or more and 20° or less.

[0252] The display device 50O in the present embodiment has a predetermined optical sheet 10H. By including an optical functional layer having a light transmission portion and a light absorption portion that extend in a predetermined direction and have a predetermined cross-section, when the display device is installed in front of the passenger seat of the vehicle, the transmittance of light in a direction inclined by ±20° in the left-right direction with respect to the normal direction can be reduced. Specifically, when the transmittance of light in the normal direction is 100%, the relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±20° in the left-right direction with respect to the normal direction, can be set to 10% or less. Therefore, it is possible to control the light emission angle in the left-right direction of the display device.

[0253] Furthermore, in a state where the light emission angle in the left-right direction is controlled, the extending direction of the light transmission portion as viewed from the normal direction has an angle θ within a predetermined range with respect to the vertical direction, enabling control of the light emission angle in the up-down direction of the display device. Therefore, the display device of the present embodiment can control the emission of video light toward the driver's side and can also control the reflection of video light on the windshield in front of the passenger seat.

[0254] 1. Surface light source device The surface light source device includes a predetermined optical sheet. The optical sheet 10H in the present embodiment includes an optical functional layer having a light transmission portion and a light absorption portion that extend in a predetermined direction and have a predetermined cross-section. As a result, when the display device 50O having the predetermined optical sheet 10H is installed in front of the passenger seat of the vehicle, when the light transmittance in the normal direction N (the third direction D3 in FIGS. 1, 3, 4, and 10) of the main surface of the optical sheet 10H is set to 100%, the relative transmittance, which is the ratio of the light transmittance in the direction inclined by ±20° from the normal direction N to the left and right directions, can be set to 10% or less. The relative transmittance of the above light is preferably 5% or less.

[0255] Furthermore, in the optical sheet of the present embodiment, when the display device is installed in front of the passenger seat of the vehicle, the extending direction of the light transmission portion as viewed from the normal direction has an angle of 1.5° or more and 20° or less with respect to the vertical direction. The angle θ may be 1.5° or more, may be 5° or more, or may be 10° or more. On the other hand, the angle θ may be 20° or less, or may be 15° or less. By the angle θ being within the above range, control of the light emission angle in the left-right direction becomes possible. In FIGS. 1 and 3, the light transmission portion 3 has an angle θ on the right side (+D1 side) with respect to the vertical direction. In this case, it is preferable that the left side (-D1 side) is the driver's seat side. On the other hand, the light transmission portion 3 may have an angle θ on the left side (-D1 side) with respect to the vertical direction. In this case, it is preferable that the right side (+D1 side) is the driver's seat side.

[0256] Other features of the optical sheet in this embodiment are the same as those in "A-1. Optical sheet (first embodiment)" above, and therefore will not be described here. Other members of the surface light source device have been described in "B-1. Surface light source device (first embodiment)" above, and therefore will not be described here.

[0257] 2. Display panels and other components The display panel and other members have been described above in the section "C-1-1. Display device (first example of first embodiment)," so a description thereof will be omitted here.

[0258] 3.Applications The display device in this embodiment is placed in front of the passenger seat of the vehicle. Fig. 8(a) is a schematic diagram of the front interior of the vehicle when the display device 50O in this embodiment is placed in front of the passenger seat of the vehicle. Fig. 8(b) is a plan view illustrating the state of the optical sheet of the display device in Fig. 8(a). In Figs. 8(a) and 8(b), the optical sheet is placed so that the left-right direction is horizontal (left-right direction of the vehicle), the up-down direction is vertical, and the thickness direction is horizontal (front-rear direction of the vehicle). However, the installation posture of the display device is not limited to this.

[0259] C-8-2. Display Device (Second Example of Eighth Embodiment) FIG. 9 is a schematic plan view and a cross-sectional view showing an example of the display device of the present embodiment. FIGS. 1, 3, 4, and 10 are schematic perspective views, cross-sectional views, and plan views showing an example of the optical sheet in the display device of the present embodiment. As shown in FIG. 9, the display device 50P of the present embodiment includes a display panel 30 and an optical sheet 10H disposed on the observer side of the display panel 30. As shown in FIGS. 1, 3, 4, and 10, the optical sheet 10H in the present embodiment includes a base material layer 1 and an optical functional layer 2 laminated on one surface of the base material layer 1. The optical functional layer 2 has a plurality of light transmission portions 3 having a predetermined cross-section and extending in one direction, and a light absorption portion 4 formed between adjacent light transmission portions 3. A predetermined cross-section of the light transmission portion 3 is trapezoidal, and the short upper base is the light incident side. As shown in FIG. 3, when the display device 50P is installed, the extending direction of the light transmission portion 3 viewed from the normal direction N has an angle of 1.5° or more and 20° or less with respect to the vertical direction.

[0260] Details of FIGS. 1, 3, and 4 are described in the section of "A-1. Optical Sheet (First Embodiment)" above, so the description here is omitted. Since FIG. 10 is described in the section of "A-3. Optical Sheet (Fifth Embodiment)" above, the description here is omitted. Further, since FIG. 9 is described in the section of "C-1-2. Display Device (Second Example of the First Embodiment)" above, the description here is omitted.

[0261] 1. Optical Sheet The optical sheet is the same as the optical sheet described in the section of "C-8-1. Display Device (First Example of the Eighth Embodiment)" above, so the description here is omitted.

[0262] 2. Display Panel and Other Members The display panel and other members are described in the section of "C-1-2. Display Device (Second Example of the First Embodiment)" above, so the description here is omitted.

[0263] 3. Use The use of the display device in the present embodiment is the same as that in "C-8-1. Display Device (First Example of the Eighth Embodiment)" above, so the description here is omitted.

[0264] Note that the present disclosure is not limited to the above-described embodiments. The above-described embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present disclosure and exhibits the same effects is included in the technical scope of the present disclosure.

Example

[0265] Examples and comparative examples are shown below to explain the present disclosure in more detail.

[0266] [Examples 1 to 18 and Comparative Examples 1 to 14] An optical sheet having a base material layer and an optical functional layer shown in FIGS. 1 to 4 was manufactured. At this time, the angle with respect to the second direction of the light transmission portion (bias angle θ), the leg inclination angle θ in the trapezoidal cross section 11 and θ 12 , the incident-side aperture ratio, the height Da of the light absorption portion, the OD value of the light absorption portion, and the refractive index difference Nt - Nr between the light transmission portion and the light absorption portion were changed as shown in Tables 1 and 2. In Sample Groups 1 to 3, the refractive index Nt of the light transmission portion was 1.57, and the refractive index difference Nr of the light absorption portion was 1.54.

[0267] Regarding the obtained optical sheet, the luminance of light was measured as follows, and the transmittance and relative transmittance were calculated.

[0268] (Measurement method) First, without placing an optical sheet, the luminance of light from a surface light source (an edge-lit surface light source using an LED as a light source) alone in the third direction D3 was measured using a viewing angle characteristic measurement device (EZ Contrast XL80 manufactured by ELDIM). Next, the surface light source (an edge-lit surface light source using an LED as a light source) was placed on the back side (optical functional layer side) of the optical sheet, and the luminance of light transmitted through the optical sheet in the third direction D3 and the luminance of light transmitted in a direction tilted ±30° toward the first direction D1 with respect to the third direction D3 were measured on the front side (substrate layer side) using a viewing angle characteristic measurement device (EZ Contrast XL80 manufactured by ELDIM). The ratio of the luminance of light transmitted through the optical sheet in the third direction D3 to the luminance of light from the surface light source alone in the third direction D3 was then calculated as the transmittance of light transmitted through the optical sheet in the third direction D3. Similarly, the ratio of the brightness of light transmitted in a direction tilted ±30° toward the first direction D1 with respect to the third direction to the brightness of light in the third direction D3 of the surface light source alone was calculated as the transmittance of light transmitted in a direction tilted ±30° toward the first direction D1 with respect to the third direction D3. Finally, the relative transmittance was calculated, which is the ratio of the transmittance of light transmitted in a direction tilted ±30° toward the first direction D1 with respect to the third direction D3 when the transmittance of light transmitted through the optical sheet in the third direction D3 is taken as 100%. The results are shown in Tables 1 and 2.

[0269] In addition, in the same manner as described above, the relative transmittance was calculated, which is the ratio of the transmittance of light transmitted in a direction inclined ±20° toward the first direction D1 relative to the third direction D3, when the transmittance of light transmitted in the third direction D3 of the optical sheet is taken as 100%.

[0270] The results of measuring the relative transmittance of the optical sheets of Example 4 and Comparative Example 8 are shown in FIGS. 12(a) and 13(a). FIG. 12(a) shows that the horizontal axis represents the viewing angle in the left-right direction (first direction D1), and the vertical axis represents the ratio of the light transmittance at each viewing angle in the left-right direction (relative transmittance) when the light transmittance at a viewing angle of 0° is set to 100%. The optical sheet of Example 4 obtained a relative transmittance of 0.5% at a viewing angle of ±30° in the first direction D1 and a relative transmittance of 5.0% at a viewing angle of ±20° in the first direction D1. On the other hand, the optical sheet of Comparative Example 8 had a relative transmittance of 17.8% at a viewing angle of ±30° in the first direction D1 and a relative transmittance of 57.8% at a viewing angle of ±20° in the first direction D1.

[0271] FIG. 13(a) shows that the horizontal axis represents the viewing angle in the up-down direction (second direction D2), and the vertical axis represents the ratio of the light transmittance at each viewing angle in the up-down direction (relative transmittance) when the light transmittance at a viewing angle of 0° is set to 100%. The optical sheet of Example 4 obtained a relative transmittance of 18% at a viewing angle of ±30° in the second direction D2. On the other hand, the optical sheet of Comparative Example 8 obtained a relative transmittance of 31.1% at a viewing angle of ±30° in the second direction D2.

[0272] [Table 1]

[0273] [Table 2]

[0274] [Table 3]

[0275] [Table 4]

[0276] The optical sheets of Example 4 and Comparative Example 8 were used in a display device, and the device was observed from the front and obliquely from a position where the horizontal viewing angle was about 30°. Fig. 12(b) shows how the display device was observed. In Comparative Example 8, video light was visible from a position where the horizontal viewing angle was about 30°, whereas in Example 4, it was confirmed that video light was not visible from a position where the horizontal viewing angle was about 30°.

[0277] Assuming the case where the optical sheets of Examples 1 to 18 and Comparative Examples 1 to 14 were used in the passenger seat display device, the presence or absence of reflection of video light on the windshield in front of the passenger seat was observed. In Comparative Example 8, reflection of video light on the windshield was observed, whereas in Example 4, it was confirmed that the reflection was suppressed (Fig. 13(b)). Also, the presence or absence of reflection on the windshield when using the optical sheets of other examples and comparative examples is shown in Table 1 and Table 2. From Table 1 and Table 2, it was confirmed that when the relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±30° to the second direction side with respect to the third direction when the transmittance of light in the third direction is 100%, is 32% or less, reflection on the windshield is suppressed.

[0278] That is, in the present disclosure, the following inventions can be provided. [1] An optical sheet including a base material layer and an optical functional layer laminated on one surface of the base material layer, wherein the optical sheet has a rectangular shape having a pair of first sides extending in a first direction and a pair of second sides extending in a second direction in a plan view, the optical functional layer has a plurality of light transmission portions having a predetermined cross section and extending in one direction, and light absorption portions formed between adjacent light transmission portions, the predetermined cross section of the light transmission portion is trapezoidal, with the short upper base being the light incident side, when the transmittance of light in a third direction orthogonal to the first direction and the second direction is 100%, the relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±20° to the first direction side with respect to the third direction, is 10% or less, An optical sheet in which the extending direction of the light-transmitting portion has an angle of 1.5° or more and 20° or less with respect to the second direction. [2] An optical sheet including a base material layer and an optical functional layer laminated on one surface of the base material layer, wherein the base material layer is a resin base material, in a plan view, the optical sheet has a rectangular shape having a pair of first sides extending in a first direction and a pair of second sides extending in a second direction, the optical functional layer has a plurality of light-transmitting portions each having a predetermined cross-section and extending in one direction, and light-absorbing portions formed between adjacent light-transmitting portions, the predetermined cross-section of the light-transmitting portion is trapezoidal, and the short upper base is on the light-incident side, the optical sheet is an optical sheet for a display device disposed in front of the passenger seat of a vehicle, An optical sheet in which the extending direction of the light-transmitting portion has an angle of 1.5° or more and 20° or less with respect to the second direction. [3] The relative transmittance, which is the ratio of the transmittance of light in a direction inclined by ±20° to the first direction side with respect to the third direction when the transmittance of light in the third direction orthogonal to the first direction and the second direction is 100%, is 10% or less. The optical sheet according to [2]. [4] The optical sheet according to any one of [1] to [3], wherein the angle formed by the interface between the light-transmitting portion and the light-absorbing portion with respect to the normal of the layer surface of the optical functional layer is 4.5° or more. [5] The optical sheet according to any one of [1] to [4], wherein the light-incident side aperture ratio of the optical functional layer is 35% or less. [6] The optical sheet according to any one of [1] to [5], wherein the height of the light-absorbing portion is 120 μm or more. [7] The optical sheet according to any one of [1] to [6], wherein the OD value of the light-absorbing portion is 3.5 or more. [8] The optical sheet according to any one of [1] to [7], wherein the difference Nt-Nr between the refractive index Nt of the light-transmitting portion and the refractive index Nr of the light-absorbing portion is 0.05 or less. [9] The optical sheet according to any one of [1] to [8], wherein the retardation of the substrate layer is 3000 nm or more.

[10] [1] to [9], and the optical sheet according to any one of [1] to [9]. a light source that emits light incident on the optical sheet.

[11]

[10] The surface light source device according to

[10] , A display device comprising: a display panel laminated on the surface light source device.

[12] A display device comprising an optical sheet and a display panel, The optical sheet includes a base layer and an optical functional layer laminated on one surface of the base layer, the optical function layer has a plurality of light-transmitting portions each having a predetermined cross section and extending in one direction, and a light-absorbing portion formed between adjacent light-transmitting portions; The predetermined cross section of the light transmitting portion is trapezoidal, and a shorter upper base is a light incident side, When the display device is installed, the optical sheet a relative transmittance, which is the ratio of light transmittance in directions tilted by ±20° to the left or right from the normal direction when the light transmittance in the normal direction to the main surface of the optical sheet is taken as 100%, of 10% or less; a display device in which the extending direction of the light transmitting portion as viewed from the normal direction forms an angle of 1.5° or more and 20° or less with respect to the vertical direction.

[13] A display device including an optical sheet and a display panel, and disposed in front of a passenger seat of a vehicle, The optical sheet includes a base layer and an optical functional layer laminated on one surface of the base layer, the substrate layer is a resin substrate, the optical function layer has a plurality of light-transmitting portions each having a predetermined cross section and extending in one direction, and a light-absorbing portion formed between adjacent light-transmitting portions; The predetermined cross section of the light transmitting portion is trapezoidal, and a shorter upper base is a light incident side, When the display device is installed in front of the passenger seat of a car, the optical sheet a display device in which the extending direction of the light transmitting portion as viewed from the normal direction of the main surface of the optical sheet forms an angle of 1.5° or more and 20° or less with respect to the vertical direction.

[14] When the display device is installed in front of the passenger seat of a car, the optical sheet The display device according to

[13] , wherein the relative transmittance, which is the ratio of the light transmittance in a direction tilted ±20° to the left or right from the normal direction when the light transmittance in the normal direction of the main surface of the optical sheet is 100%, is 10% or less.

[15] The display device according to any one of

[12] to

[14] , wherein the display device comprises a surface light source device, and the surface light source device includes the optical sheet.

[16] The display device according to any one of

[12] to

[14] , wherein the optical sheet is disposed on the viewer side of the display panel.

[17] The display device according to

[16] , which is an organic electroluminescence display device.

[18] The display device according to any one of

[12] to

[16] , which is a liquid crystal display device. [Explanation of symbols]

[0279] 1... Base material layer 2… Optical functional layer 3... Light transmitting part 4... Light absorbing part 10... Optical sheet 15... LCD panel 20… Surface light source device 21…Light guide plate 25… light source 26... Light diffuser 27… Prism layer 28… Reflective polarizing plate 50… Display device

Claims

1. An optical sheet comprising a base material layer and an optical functional layer laminated on one surface of the base material layer, The optical sheet has a rectangular shape having a pair of first sides extending in a first direction and a pair of second sides extending in a second direction in a plan view, The optical functional layer has a plurality of light transmission portions extending in one direction with a predetermined cross section and a light absorption portion formed between adjacent light transmission portions, The predetermined cross section of the light transmission portion is trapezoidal, and the short upper base is on the light incident side, When the light transmittance in a third direction orthogonal to the first direction and the second direction is 100%, the relative transmittance, which is the ratio of the light transmittance in a direction inclined by ±20° to the first direction side with respect to the third direction, is 10% or less, An optical sheet, wherein the extending direction of the light transmission portion has an angle of 1.5° or more and 20° or less with respect to the second direction.

2. An optical sheet comprising a base material layer and an optical functional layer laminated on one surface of the base material layer, The base material layer is a resin base material, The optical sheet has a rectangular shape having a pair of first sides extending in a first direction and a pair of second sides extending in a second direction in a plan view, The optical functional layer has a plurality of light transmission portions extending in one direction with a predetermined cross section and a light absorption portion formed between adjacent light transmission portions, The predetermined cross section of the light transmission portion is trapezoidal, and the short upper base is on the light incident side, The optical sheet is an optical sheet for a display device disposed in front of the passenger seat of a vehicle, An optical sheet, wherein the extending direction of the light transmission portion has an angle of 1.5° or more and 20° or less with respect to the second direction.

3. The optical sheet according to claim 2, wherein when the light transmittance in a third direction orthogonal to the first direction and the second direction is 100%, the relative transmittance, which is the ratio of the light transmittance in a direction inclined by ±20° to the first direction side with respect to the third direction, is 10% or less.

4. The optical sheet according to any one of claims 1 to 3, wherein the angle formed by the interface between the light transmission portion and the light absorption portion with respect to the normal of the layer surface of the optical functional layer is 4.5° or more.

5. The optical sheet according to any one of claims 1 to 3, wherein the light incident side opening ratio of the optical functional layer is 35% or less.

6. The optical sheet according to any one of claims 1 to 3, wherein the height of the light absorption portion is 120 μm or more.

7. The optical sheet according to any one of claims 1 to 3, wherein the OD value of the light absorption part is 3.5 or more.

8. The optical sheet according to any one of claims 1 to 3, wherein the difference Nt - Nr between the refractive index Nt of the light transmission part and the refractive index Nr of the light absorption part is 0.05 or less.

9. The optical sheet according to any one of claims 1 to 3, wherein the retardation of the base material layer is 3000 nm or more.

10. An optical sheet according to any one of claims 1 to 3, and a light source that emits light incident on the optical sheet, a surface light source device.

11. The surface light source device according to claim 10, and a display panel laminated on the surface light source device, a display device.

12. A display device including an optical sheet and a display panel, wherein the optical sheet includes a base material layer and an optical function layer laminated on one surface of the base material layer, the optical function layer has a plurality of light transmission parts extending in one direction having a predetermined cross section, and a light absorption part formed between adjacent light transmission parts, the predetermined cross section of the light transmission part is trapezoidal, and the short upper base is the light incident side, when the display device is installed, the optical sheet has a relative transmittance, which is a ratio of the light transmittance in a direction inclined by ±20° in the left - right direction from the normal direction, of 10% or less when the light transmittance in the normal direction of the main surface of the optical sheet is set to 100%, a display device, wherein the extending direction of the light transmission part as viewed from the normal direction has an angle of 1.5° or more and 20° or less with respect to the vertical direction.

13. A display device including an optical sheet and a display panel, and being disposed in front of the passenger seat of a vehicle, wherein the optical sheet includes a base material layer and an optical function layer laminated on one surface of the base material layer, the base material layer is a resin base material, the optical function layer has a plurality of light transmission parts extending in one direction having a predetermined cross section, and a light absorption part formed between adjacent light transmission parts, the predetermined cross section of the light transmission part is trapezoidal, and the short upper base is the light incident side, when the display device is installed in front of the passenger seat of the vehicle, a display device, wherein the extending direction of the light transmission part as viewed from the normal direction of the main surface of the optical sheet has an angle of 1.5° or more and 20° or less with respect to the vertical direction.

14. When the display device is installed in front of the passenger seat of a vehicle, The display device according to claim 13, wherein a relative transmittance, which is a ratio of the light transmittance in a direction inclined by ±20° from the normal direction to the left and right directions when the light transmittance in the normal direction of the main surface of the optical sheet is 100%, is 10% or less.

15. The display device according to any one of claims 12 to 14, wherein the display device includes a surface light source device, and the surface light source device includes the optical sheet.

16. The display device according to any one of claims 12 to 14, wherein the optical sheet is disposed on the observer side of the display panel.

17. The display device according to claim 16, which is an organic electroluminescence display device.

18. The display device according to any one of claims 12 to 14, which is a liquid crystal display device.

Images