JP2016151710A - Optical sheet, video source unit, and video display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet that has light-shielding performance and can maintain high efficiency of use of light.SOLUTION: There is provided an optical sheet (20) comprising a plurality of layers, and including a substrate layer (25), a plurality of light transmission parts (22) that are laminated on one face of the substrate layer and arranged along a layer surface of the substrate layer so as to transmit light, and an optical function layer (21) that includes light absorption parts (23) that are arranged between the adjacent light transmission parts so as to absorb light. On a cross section in the layer thickness direction of the optical function layer, the cross-sectional area of the light transmission part to the total cross-sectional area of the adjacent one light transmission part and light absorption part is 78.2% or more and 88.5% or less.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an optical sheet that controls light emitted from a light source and emits the light toward an observer, an image source unit including the optical sheet, and an image display device.

  In video display devices that emit images to an observer, such as liquid crystal displays, rear projection display devices, display devices using organic EL, and FEDs, the quality of the light source and the light emitted from the light source is improved. An optical sheet including a plurality of layers having various functions for providing to an observer is provided.

  For example, Patent Document 1 is disclosed as such an optical sheet. The optical sheet (light control film) described in Patent Document 1 includes a transmission area arranged in parallel along the sheet surface so that light can be transmitted, and an absorption area arranged in parallel so as to absorb light between the transmission areas. . It is disclosed that the width of the narrowest part of the transmission area and the pitch of the transmission area have a predetermined relationship.

Special table 2012-530938 gazette

  When having such a light absorption part (absorption area), the light which causes a malfunction can be absorbed by the light absorption part, and an appropriate light shielding property is provided. However, on the other hand, since light is absorbed, there is a problem that the light use efficiency is lowered. Although a technique such as Patent Document 1 is disclosed, the conventional technique is not always sufficient from the viewpoint of obtaining a high light utilization efficiency while providing a certain level of light shielding performance.

  Therefore, in view of the above problems, an object of the present invention is to provide an optical sheet that can maintain high light use efficiency while having light shielding properties. In addition, an image source unit and an image display device including the optical sheet are provided.

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiment.

  The invention according to claim 1 is an optical sheet (20) having a plurality of layers, which is laminated on one surface of the base material layer (25) and the base material layer so as to transmit light. An optical functional layer (21) having a plurality of light transmission parts (22) arranged along the layer surface of the light absorption part, and a light absorption part (23) arranged to absorb light between adjacent light transmission parts; And the cross-sectional area of the light transmission part with respect to the total cross-sectional area of one adjacent light transmission part and light absorption part in the layer thickness direction cross section of the optical functional layer is 78.2% or more and 88.5% or less The optical sheet.

  According to a second aspect of the present invention, in the optical sheet (20) according to the first aspect, the light transmissive portion (22) has a trapezoidal cross section in the layer thickness direction.

  The invention according to claim 3 is a surface light source device (11), the optical sheet (20) according to claim 1 or 2 disposed on the light emitting side of the surface light source device, and a surface light source with the optical sheet interposed therebetween. A video source unit (5) comprising a liquid crystal panel (12) arranged on the opposite side of the device.

  According to a fourth aspect of the present invention, in the video source unit (5) according to the third aspect, the optical sheet (20) is laminated on the base layer (15) and one surface of the base layer, and Optical having a plurality of light transmission parts (22) arranged along the layer surface of the base material layer so as to transmit light and a light absorption part (23) arranged so as to absorb light between adjacent light transmission parts A light transmitting portion having a trapezoidal cross section, a short upper base facing the surface light source device side, a long lower bottom facing the liquid crystal panel side, and a light absorbing portion having a trapezoidal cross section It is assumed that the lower base is arranged with the surface light source device side and the short upper base faces the liquid crystal panel side.

  Invention of Claim 5 is a video display apparatus (1) provided with a housing | casing (2) and the video source unit (5) of Claim 3 or 4 arrange | positioned inside a housing | casing. .

  According to the present invention, it is possible to maintain high light use efficiency while providing light shielding properties.

1 is an external perspective view of a video display device 1. FIG. 4 is an exploded perspective view of the video source unit 5. FIG. 3 is a cross-sectional view illustrating a layer configuration of a video source unit 5. FIG. FIG. 3 is an enlarged view paying attention to the optical function layer 21. FIG. 5A illustrates the optical functional layer 21 ′, and FIG. 5B illustrates the optical functional layer 21 ″. FIG. 3 is a diagram illustrating the form of the optical function layer of Example 1. It is a figure explaining the form of the optical function layer of Example 2. FIG. FIG. 6 is a diagram illustrating the form of an optical function layer of Example 3. It is a figure explaining the form of the optical function layer of Example 4. FIG. It is a figure explaining the form of the optical function layer of Example 5. FIG. It is a figure explaining the form of the optical function layer of Example 6. FIG. It is a figure explaining the form of the optical function layer of the comparative example 1. FIG. It is a figure explaining the form of the optical function layer of the comparative example 2. It is a figure explaining the form of the optical function layer of the comparative example 3. FIG.

  The present invention will be described below based on embodiments shown in the drawings. However, the present invention is not limited to the embodiment. Here, since the elements provided in the present invention are actually very fine and many thin layers, for ease of understanding, some of the elements are shown by being deformed or enlarged. In addition, elements are denoted by reference numerals, but some of the repeated reference numerals may be omitted for the sake of clarity.

FIG. 1 is a perspective view showing an image display apparatus 1 including an image source unit 5, illustrating one embodiment. In FIG. 1, the right side of the page is the observer side. Here, the video display device 1 of the present embodiment is an in-vehicle video display device, and includes, for example, a car navigation device. The video display device 1 includes a housing 2, and a video source unit 5 is built inside the housing 2.
The housing 2 is a member that forms an outer shell of the video display device 1 and that accommodates most of the members constituting the video display device. The housing 2 has an opening, and a so-called screen portion of the image source unit 5 is exposed from the opening so that the image can be viewed. In addition, the video display device 1 includes various known constituent members for functioning as a video display device.

  FIG. 2 is an exploded perspective view of the video source unit 5. In FIG. 2, for ease of understanding, a part of the layers constituting the video source unit is shown separately, but in actuality, they are stacked by being directly overlapped (see FIG. 3). FIG. 3 is a cross-sectional view in the thickness direction including a line indicated by III-III in FIG. 2 (a line in the vertical direction). When the video source unit 5 is arranged in the video display device 1, the right side of the paper in FIGS. 2 and 3 is the observer side, and the left side of the paper in FIGS. 2 and 3 is the light source side.

  The video source unit 5 includes a video source 10 and a functional layer 30 disposed on the video output side (that is, the observer side) of the video source 10.

  In this embodiment, the video source 10 includes the liquid crystal panel 12. Specifically, the video source 10 includes a surface light source device 11, an optical sheet 20, and a liquid crystal panel 12. That is, in this embodiment, the optical sheet 20 is disposed between the surface light source device 11 and the liquid crystal panel 12.

Here, the surface light source device 11 and the liquid crystal panel 12 may have a known structure.
For example, with respect to the surface light source device 11, a reflection sheet, a light guide plate (a light emission source is disposed on the side surface) from the light source side (left side in FIG. 3) to the viewer side (right side in FIG. 3), Examples include a surface light source device in which a diffusion sheet, a lens (prism) sheet, and a reflective polarizing sheet are laminated in this order.
On the other hand, the liquid crystal panel 12 is laminated in the order of a polarizing film, a glass substrate, a liquid crystal layer, a glass substrate, and a polarizing film from the light source side (left side of FIG. 3) to the viewer side (right side of FIG. 3). Liquid crystal panels.

  In this embodiment, the optical sheet 20 is disposed between the surface light source device 11 and the liquid crystal panel 12 on the light emitting side of the surface light source device 11 and includes a plurality of layers. In this embodiment, the optical sheet 20 includes an optical functional layer 21 and a base material layer 25 from the surface light source device 11 side. Each layer will be described below. Here, for convenience, the base material layer 25 will be described first, and then the optical function layer 21 will be described.

The base material layer 25 is a layer serving as a base material for forming the optical functional layer 21 on one surface thereof. The base material layer 25 has translucency and supports the optical functional layer 21 so as to prevent deformation. From this point of view, specific examples of the material constituting the base material layer 25 include, for example, transparent resins mainly composed of acrylic, styrene, polycarbonate, polyethylene terephthalate (PET), acrylonitrile, triacetylcellulose (TAC), epoxy acrylate, Examples thereof include urethane acrylate-based reactive resins (ionizing radiation curable resins and the like).
Among these, it is preferable to use TAC, methacrylic resin, and polycarbonate with low birefringence in consideration of the combination with the liquid crystal panel. Furthermore, it is desirable to use a polycarbonate having a high glass transition point in applications that require high heat resistance such as in-vehicle use. Specifically, the glass transition point of polycarbonate is 143 ° C., which is generally suitable for in-vehicle applications that require durability at 105 ° C.

  Although the thickness of the base material layer 25 is not specifically limited, It is preferable that they are 25 micrometers or more and 300 micrometers or less. If the thickness of the base material layer 25 is out of this range, there is a risk of causing problems in workability. For example, wrinkles tend to occur when the base material layer 25 is thinner than 25 μm. Moreover, when the base material layer 25 becomes thicker than 300 micrometers, winding of the optical sheet 20 will become difficult.

  Moreover, the surface of the base material layer 25 that does not contact the optical function layer 21 may be a rough surface. When a rough surface is formed, the surface roughness of the rough surface is preferably from 0.1 μm to 0.2 μm in terms of Ra (μm) (JIS B 0601 (2001) arithmetic average roughness). By making the surface roughness within this range, when the optical sheet 20 is brought into contact with another layer, generation of interference fringes due to so-called optical adhesion and irregularities based on this roughness can be easily seen by human eyes. Occurrence of defects in appearance such as scintillation (so-called screen glare) can be suppressed.

  In this embodiment, the optical functional layer 21 has a function of absorbing a part of the image light by changing the direction of the image light to the front direction so that the image light emitted from the image source 10 is not reflected on the windshield of the car. . FIG. 4 shows an enlarged part of FIG. 3 while paying attention to the optical functional layer 21.

  In this embodiment, the optical functional layer 21 has a cross section shown in FIGS. 3 and 4 and a shape extending in the back / front direction of the paper with respect to the paper. In the present embodiment, in the posture in which the video display device 1 is installed in the vehicle, the extending direction is a horizontal direction. This prevents the image light from being reflected on the windshield as will be described later.

  In the cross section shown in FIGS. 3 and 4, the optical functional layer 21 includes a trapezoidal light transmission part 22 and a light absorption part 23 having a trapezoidal cross section formed between two adjacent light transmission parts 22. I have. Therefore, in the present embodiment, the light transmission unit 22 and the light absorption unit 23 are alternately arranged in the vertical direction in a posture in which the video display device 1 is installed in the vehicle.

  The light transmission part 22 is a part whose main function is to transmit light. In this embodiment, in the cross section shown in FIGS. 3 and 4, the base layer 25 side (observer side) has a long lower bottom, and vice versa. It is an isosceles trapezoid having a short upper base on the side (surface light source device 11 side). The light transmitting portions 22 extend along the layer surface of the base material layer 25 while maintaining the cross section, and are arranged at intervals in a direction different from the extending direction. An interval having a trapezoidal cross section is formed between the adjacent light transmission portions 22. Therefore, the interval has a trapezoidal cross section having a long lower base on the upper base side of the light transmitting portion 22 and a short upper base on the lower base side of the light transmitting portion 22, and is filled with necessary materials described later. As a result, the light absorbing portion 23 is formed. In addition, in this embodiment, it has the connection part 24 which connects the adjacent light transmission part 22 by a long lower bottom side.

  The light transmission portion 22 has a refractive index of Nt. Such a light transmission part 22 can be formed by hardening a transmission part constituent composition. The value of the refractive index Nt is not particularly limited. However, as will be described later, the refractive index is 1.55 or more from the viewpoint of appropriately total reflection of light at the interface with the light absorbing portion 23 on the slope of the trapezoidal cross section. It is preferable. More preferably, it is 1.56 or more. However, since a material with a refractive index that is too high is likely to break, the refractive index is preferably 1.61 or less.

  Here, examples of the composition constituting the light transmitting portion include ionizing radiation curable resins such as ultraviolet rays such as epoxy acrylate, urethane acrylate, polyether acrylate, polyester acrylate, and polythiol. it can.

  The light absorbing portions 23 are arranged at the above-described intervals formed between the adjacent light transmitting portions 22 and have a cross-sectional shape similar to the cross-sectional shape of the intervals. Therefore, it becomes an isosceles trapezoid with the short upper base facing the base material layer 25 side (observer side) and the long lower base facing the opposite side (surface light source device 11 side). And the light absorption part 23 is comprised so that light can be absorbed while the refractive index is set to Nr. Specifically, light absorbing particles are dispersed in a binder having a refractive index of Nr. The refractive index Nr is a refractive index lower than the refractive index Nt of the light transmission part 22. The value of the refractive index Nr is not particularly limited, but is preferably 1.50 or less, more preferably 1.49 or less. Further, from the viewpoint of easy availability, 1.47 or more is preferable.

  The difference in refractive index between the refractive index Nt of the light transmitting portion 22 and the refractive index Nr of the light absorbing portion 23 is not particularly limited, but is preferably 0.05 or more. On the other hand, the upper limit of the refractive index difference is not particularly limited, but the refractive index difference is preferably 0.14 or less from the viewpoint of material availability.

  Although the material used as a binder here is not specifically limited, For example, mention may be made of photocurable resins such as urethane (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, and butadiene (meth) acrylate. it can.

  The light absorbing particles are preferably light absorbing colored particles such as carbon black. However, the light absorbing particles are not limited to these, and colored particles that selectively absorb a specific wavelength in accordance with the characteristics of the image light. May be used. Specific examples include organic fine particles colored with metal salts such as carbon black, graphite, and black iron oxide, dyes, pigments, colored glass beads, and the like. In particular, colored organic fine particles are preferably used from the viewpoints of cost, quality, availability, and the like. The average particle diameter of the colored particles is preferably 0.01 μm or more and 20 μm or less.

Further, in the present invention, the total cross-sectional area of one adjacent light transmission part 22 and light absorption part 23 (the cross-sectional area of the cross section shown in FIG. 4, in the direction in which the light transmission part 22 and the light absorption part 23 extend). The ratio of the cross-sectional area of the light transmitting portion 22 to the cross-sectional area in the direction perpendicular to the cross-sectional area (light transmitting cross-sectional area ratio) is 78.2% or more and 88.5% or less. Here, as represented by S1 in FIG. 4, the cross-sectional area of the light transmitting portion 22 is the light transmitting portion 22 existing between the adjacent light absorbing portions 23, and in this embodiment, the cross-sectional area is an isosceles trapezoid. Further, the cross-sectional area of the light absorbing portion 23 is an isosceles trapezoidal cross-sectional area in this embodiment as represented by S2 in FIG.
As a result, the light utilization efficiency can be set to a high level while having a predetermined light shielding property. If the cross-sectional area ratio of the light transmission part is smaller than 78.2%, the utilization efficiency of the light supplied from the light source is lowered. On the other hand, if the cross-sectional area ratio of the light transmission part exceeds 88.5%, the light shielding property is lowered and the light to be excluded is also transmitted. In addition, if the cross-sectional area ratio of the light transmitting portion exceeds 88.5%, the light absorbing portion becomes further fine, and it becomes difficult to manufacture a precise light absorbing portion.

  In addition, although not specifically limited, for example, the light transmitting portion 22 and the light absorbing portion 23 are formed as follows. That is, it is preferable that the pitch of the light transmission part 22 and the light absorption part 23 represented by Pk in FIG. 3 is 30 μm or more and 100 μm or less. Further, the angle formed by the interface on the oblique side of the light absorbing portion 23 and the light transmitting portion 22 indicated by θk in FIG. 4 and the normal line of the layer surface of the optical functional layer 21 is 0 ° or more and 10 ° or less. preferable. And it is preferable that the thickness of the light absorption part 23 shown by Dk in FIG. 3 is 60 micrometers or more and 150 micrometers or less. By being within these ranges, the balance between light transmission and light absorption is further improved.

  In this embodiment, an example in which the interface (leg part) between the light transmitting part 22 and the light absorbing part 23 is straight in the cross section is shown. However, the present invention is not limited to this, but a polygonal line shape, a convex curved surface, or a concave curved surface shape. Etc. Moreover, the cross-sectional shape may be the same in the some light transmission part 22 and the light absorption part 23, and a different cross-sectional shape may have predetermined regularity.

FIG. 5 shows an example in which the legs in the trapezoidal cross section are asymmetric. FIG. 5 corresponds to FIG. FIG. 5A shows an example of the optical functional layer 21 ′, and FIG. 5B shows an example of the optical functional layer 21 ″.
The optical function layer 21 ′ shown in FIG. 5A has a light transmission part 22 ′ and a light absorption part 23 ′, and the concept of the light transmission part area ratio is the same as that of the optical function layer 21. As can be seen from FIG. 5A, the present example further has a feature in the leg portion in the trapezoidal cross section of the light absorbing portion 23 ′. In the light absorbing portion 23 ′, the angle formed between the two leg portions and the normal to the layer surface of the optical functional layer 22 ′ is different. More specifically, the angle formed by the lower leg portion 23 ′ a in the posture in which the video display device is installed is smaller than the angle formed by the upper leg portion 23 ′ b. More preferably, the angle formed by the leg 23′a is 0 ° (that is, the leg 23′a is parallel to the normal to the layer surface of the optical function layer 23 ′). Thereby, it is possible to efficiently suppress upward light (image light), and it is possible to further suppress reflection on the windshield in the case of in-vehicle use.
On the other hand, the optical function layer 21 ″ shown in FIG. 5B has a light transmission part 22 ″ and a light absorption part 23 ″, and the concept of the light transmission part area ratio is the same as that of the optical function layer 21. In this configuration, the relationship between the inclination of the legs is inverted upside down with respect to the optical functional layer 21 '. According to this, the amount of image light emitted obliquely upward increases, but the reflection on the windshield does not cause a problem. In some cases, a bright image can be observed even from a perspective from above.

Such an optical sheet 20 is produced as follows, for example.
First, the light transmission part 22 is formed on one surface of the base material layer 25. This inserts the base material sheet used as the base material layer 25 between the mold roll which has the shape which can transfer the shape of the light transmission part 22 on the surface, and the nip roll arrange | positioned so as to oppose this. And a mold roll and a nip roll are rotated, supplying the composition which comprises a light transmissive part between a base material sheet and a mold roll. As a result, a groove corresponding to the light transmitting portion formed on the surface of the mold roll (a shape obtained by reversing the shape of the light transmitting portion) is filled with the composition that constitutes the light transmitting portion, and the composition becomes the surface of the mold roll. It will be along the shape.

  Light for curing with a light irradiation device is irradiated from the substrate sheet side to the composition constituting the light transmission portion sandwiched between the mold roll and the substrate sheet and filled therein. Thereby, a composition can be hardened and the shape can be fixed. And the base material layer 25 and the shape | molded light transmission part 22 are released from a metal mold | die roll with a mold release roll.

  Next, the light absorption part 23 is formed. In order to form the light absorption part 23, first, the composition constituting the light absorption part is filled in the interval between the light transmission parts 22 formed above. Thereafter, the surplus composition is scraped off with a doctor blade or the like. Then, the remaining composition is cured by irradiating ultraviolet rays from the light transmitting portion 22 side to form the light absorbing portion 23.

  Examples of the functional layer 30 include known layers having various functions arranged on the viewer side from the liquid crystal panel. Examples thereof include an antireflection layer, an antiglare layer, and a hard coat layer.

  The video source unit 5 having the above-described configuration can be manufactured as follows, for example. That is, the produced optical sheet 20 is arranged on the light emitting side of the surface light source device 11 so that the side opposite to the base material layer 25 faces the surface light source device 11 side, and the liquid crystal panel 12 is placed on the viewer side of the optical sheet 20. The functional layer 30 is laminated.

  The video display unit 1 can be obtained by placing the video source unit 5 configured as described above in the housing 2 and arranging the functional layer 30 side to be an observer side. In that case, an electric circuit, a power supply circuit, etc. for operating the video source unit 5 are also provided if necessary.

  Such a video display device is disposed in the vehicle and operates, for example, as follows. This will be described with an example of the optical path. However, the optical path example is conceptual for explanation, and does not strictly represent reflection or refraction.

  When the video display device 1 is operated, illumination light is emitted from the surface light source device 11 as shown in FIG. The light L10 emitted from the surface light source device 11 passes through the optical sheet 20 without reaching the interface between the light transmission part 22 and the light absorption part 23, and obtains and transmits video information through the liquid crystal panel 12, and also passes through the functional layer 30. Then, the viewer can reach the viewer side and observe the image light.

  The light L11 emitted from the surface light source device 11 reaches the interface between the light transmission part 22 and the light absorption part 23, and is totally reflected by the relationship between the refractive index difference between them and the angle of incidence on the interface, and is displayed on the liquid crystal panel 12 as video information. Is transmitted, and the functional layer 30 is also transmitted and emitted to the viewer side. At this time, since the interface between the light transmitting portion 22 and the light absorbing portion 23 is inclined as described above with respect to the normal line of the light exit surface of the optical sheet 20, the direction of the light L11 is changed downward. . This prevents reflection on the windshield. Further, since the light L11 is directed in the front direction, it contributes to the improvement of the front luminance of the image light.

  Further, the light L12 emitted from the surface light source device 11 reaches the interface between the light transmission part 22 and the light absorption part 23, and is transmitted through the interface due to the difference in refractive index between them and the incident angle to the interface, thereby absorbing light. Absorbed by part 23. This prevents the upward light from traveling and prevents the image from being reflected on the windshield.

  And in this invention, since the light transmission part cross-sectional area ratio is comprised as mentioned above, the light radiate | emitted to the observer side like light L10 and light L11 is absorbed, absorbing stray light like light L12. It can be obtained efficiently, and the light utilization efficiency can be kept high.

  As examples, optical sheets (Examples 1 to 6) according to six examples in which the cross-sectional shapes of the light transmission part and the light absorption part were changed were produced, and the light use efficiency was examined. In addition, as comparative examples, optical sheets according to three examples (Comparative Examples 1 to 3) were produced, and light utilization efficiency was similarly examined.

Example 1
In Example 1, an optical sheet including an optical functional layer having the cross-sectional shape shown in FIG. 6 was produced. This optical sheet was formed from an optical functional layer and a base material layer, and was produced by the method described above. More specifically, it is as follows.
A polycarbonate resin having a thickness of 130 μm was used as the base material layer.
The light transmissive part was made of UV curable urethane acrylate having a refractive index of 1.56, and the light transmissive part had an isosceles trapezoidal cross section with an upper base of 29 μm, a lower base of 35 μm, and a height of 102 μm.
The binder of the light absorbing portion was an ultraviolet curable urethane acrylate having a refractive index of 1.49, and 25% by mass of acrylic beads containing carbon black was contained therein. The cross section of the light absorption part is an isosceles trapezoid, and the upper base is 4 μm, the lower base is 10 μm, and the height is 102 μm.
The thickness of the connecting portion (Lk in FIG. 3) was 25 μm.

  The above optical sheet was mounted on a 6.5-inch liquid crystal display device (manufactured by Sharp Corporation, LQ65T5GG03) to obtain a liquid crystal display device. More specifically, an optical sheet is disposed on the light exit surface side of a surface light source device including a light guide plate, a prism sheet, a light diffusing film, and a reflective polarizing plate having a light source disposed on the side surface, and the light output of the optical sheet A liquid crystal panel was placed on the surface side.

(Example 2)
Example 2 is the same as Example 1 except that the cross-sectional shapes of the light transmission part and the light absorption part are changed as shown in FIG.

(Example 3)
Example 3 is the same as Example 1 except that the cross-sectional shapes of the light transmission part and the light absorption part are changed as shown in FIG.

Example 4
The fourth embodiment is an example in which the inclination angles of the two leg portions of the light transmitting portion and the light absorbing portion are different from the example shown in FIG. Specifically, the cross-sectional shapes of the light transmission part and the light absorption part were changed as shown in FIG. Here, the inclination angle of the leg 23′a is 0 ° (that is, the leg 23′a is parallel to the normal to the layer surface of the optical sheet). Others are the same as in the first embodiment.

(Example 5)
Example 5 is the same as Example 4 except that the cross-sectional shapes of the light transmission part and the light absorption part are changed as shown in FIG.

(Example 6)
Example 6 is the same as Example 4 except that the cross-sectional shapes of the light transmission part and the light absorption part are changed as shown in FIG.

(Comparative Example 1)
Comparative Example 1 is the same as Example 1 except that the cross-sectional shapes of the light transmission part and the light absorption part are changed as shown in FIG. Here, the reference numerals used in FIGS. 12 to 14 mean the optical function layer 121, the light transmission part 122, and the light absorption part 123, respectively.

(Comparative Example 2)
Comparative Example 2 is the same as Comparative Example 1 except that the cross-sectional shapes of the light transmission part and the light absorption part are changed as shown in FIG.

(Comparative Example 3)
Comparative Example 3 is the same as Comparative Example 1 except that the cross-sectional shapes of the light transmission part and the light absorption part are changed as shown in FIG.

  For the liquid crystal display devices according to Examples 1 to 6 and Comparative Examples 1 to 3 manufactured as described above, the normal direction of the optical sheet is set to 0 ° using the EZ contrast (manufactured by ELDIM), and ± from the normal direction and the normal line. Luminance was measured at positions tilted every 10 ° up to 80 °. And the luminance integral value was obtained. Therefore, it can be said that the larger the luminance integrated value is, the more light is emitted and the higher the light utilization efficiency.

  On the other hand, the light-shielding property uses EZ contrast (manufactured by ELDIM), and the brightness is measured at a position inclined every 10 ° from the normal direction and ± 80 ° to ± 80 ° with the normal direction of the optical sheet as 0 °. did. And the brightness | luminance of 45 degrees (average of 40 degrees and 50 degrees) was measured with respect to 100% of front brightness | luminance, and it expressed with percentage. And when the value was 10% or less, the light shielding property was considered good.

Table 1 shows characteristic shapes other than the above in the light transmission part and the light absorption part, and measurement results.
“Light transmission section cross-sectional area ratio (%)” is a percentage of the cross-sectional area of the light transmission sections 22 and 122 with respect to the total cross-section area of one adjacent light transmission section 22 and 122 and the light absorption sections 23 and 123. It is represented by. That is, in the cross section shown in FIG. 6 to FIG. 14, it can be calculated by “area of one light transmitting portion / (area of one light transmitting portion + 1 area of one light absorbing portion)”.
“Aperture ratio (%)” is the ratio of the light transmitting portions 22 and 122 per pitch on the light incident side of the surface of the optical function layer (in this example, the upper bottom side of the light transmitting portions 22 and 122). It is an area ratio. That is, in the cross section shown in FIG. 6 to FIG. 14, “the length of the upper base of one light transmitting portion / (the length of the upper base of one light transmitting portion + 1 the length of the lower base of one light absorbing portion)”. Can be calculated.
“Integral luminance” and “light shielding” are as described above.

  As can be seen from Table 1, each of Examples 1 to 6 has higher integrated luminance and higher light utilization efficiency than Comparative Examples 1 to 3. Here, for example, as can be seen from the comparison between Example 1 and Comparative Example 2, even when the aperture ratio is substantially the same, the integrated luminance is greatly different. Further, the light-shielding property was good in all examples of 10% or less.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 5 Image source unit 10 Image source 11 Surface light source apparatus 12 Liquid crystal panel 20 Optical sheet 21 Optical functional layer 22 Light transmission part 23 Light absorption part 25 Base material layer

Claims (5)

An optical sheet having a plurality of layers,
A base material layer;
Stacked on one surface of the base material layer and capable of absorbing light between a plurality of light transmitting portions arranged along the layer surface of the base material layer so as to transmit light, and the adjacent light transmitting portions An optical functional layer having a light absorption portion arranged,
In the cross section in the layer thickness direction of the optical function layer, the cross-sectional area of the light transmission part with respect to the total cross-sectional area of one adjacent light transmission part and the light absorption part is 78.2% or more and 88.5% or less. is there,
Optical sheet.   The optical sheet according to claim 1, wherein a cross section in the layer thickness direction of the light transmission portion is a trapezoid. A surface light source device;
The optical sheet according to claim 1 or 2, which is disposed on a light emitting side of the surface light source device,
An image source unit comprising: a liquid crystal panel disposed on the opposite side of the surface light source device with the optical sheet interposed therebetween. The optical sheet is
A base material layer;
Stacked on one surface of the base material layer and capable of absorbing light between a plurality of light transmitting portions arranged along the layer surface of the base material layer so as to transmit light, and the adjacent light transmitting portions An optical functional layer having a light absorption portion arranged,
The light transmission part has a trapezoidal cross section, the short upper base faces the surface light source device side, the long lower base faces the liquid crystal panel side, the light absorption part has a trapezoidal cross section, and the long lower base is the surface light source. The video source unit according to claim 3, wherein the apparatus side and the short upper base are arranged facing the liquid crystal panel side. A housing,
A video display device comprising: the video source unit according to claim 3 or 4 disposed inside the housing.

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