JP5007550B2 - Optical sheet - Google Patents

Description

  The present invention relates to an optical sheet used in video providing devices such as a plasma television, a liquid crystal display device, and a projection screen, and more particularly to an optical sheet that is less likely to be cracked during handling such as transportation and cutting.

  Optical sheets used for plasma televisions, liquid crystal display devices, projection screens, etc., adjust the contrast, viewing angle, optical path, etc. so that the light (video light) from the light source is appropriate and easy for the observer to see. It is a sheet that can. Such an optical sheet has a laminated structure formed of a plurality of layers having respective functions, and the respective layers are bonded by any means.

  Of the laminated structure of the optical sheets, at least one layer is a sheet having an optical function (hereinafter sometimes referred to as “optical function sheet”), and prisms and the like are arranged. As an example, the layer configuration of the optical sheet 110 is schematically shown in FIG. The optical sheet 110 includes a separator 111, an adhesive layer 112, a PET film layer 113, an optical function sheet layer 114, and a protective film 117 which are laminated in this order. Among them, the optical function sheet layer 114 further includes prism portions 115, 115,... Having a substantially trapezoidal cross section, and light absorbing portions 116 having a triangular cross section disposed between the prism portions 115, 115,. 116,...

  In addition to the above, the optical sheet includes an optical sheet in which an optical functional sheet layer having a lens having a top portion in a cross section such as a lenticular lens and a fullnel lens is laminated. With respect to general optical sheets including these, there has been a problem that the optical functional sheet layer is damaged or damaged due to, for example, long-term transportation.

On the other hand, Patent Document 1 discloses that the above problem is solved by setting the glass transition temperature, the equilibrium elastic modulus, and the like of the lenticular lens and the fullnel lens in a predetermined range.
JP 2003-313445 A

  However, the invention described in Patent Document 1 is for preventing permanent deformation caused by contact of a lens having a top portion such as a lenticular lens and a fullnel lens, particularly at the top portion. That is, the invention is an invention in which the top part comes into contact with the lenticular lens and the full-lens lens even when they are crushed by long-time transportation or the like, and no damage is caused. On the other hand, the damage that occurs in the optical functional sheet layer having no top as shown in FIG. 8 is different from this. Specifically, the prism portions 115, 115,... In FIG. 8 may be cracked along the prism portions 115, 115,.

  Then, this invention makes it a subject to provide the optical sheet which can prevent malfunctions, such as a breakage, at the time of handling at the time of transportation, a cutting | disconnection, etc.

  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.

Invention of Claim 1 is an optical sheet (10) provided with the layer which controls and radiate | emits the incident light, Comprising: The base material layer (13) which has a polyester-type resin as a main component, A prism portion (15, 15,...) Capable of transmitting light and a light absorbing portion (16, 16,...) Capable of absorbing light in a cross section that is laminated on one surface and orthogonal to the light incident surface. An optical function sheet layer (14) alternately arranged along the sheet surface, and an adhesive layer disposed on the light incident side and / or the light exit side, wherein the prism portion of the optical function sheet layer has a tensile breaking point The problem is solved by providing an optical sheet comprising a resin having an elongation of 14.5% or more and 45.6% or less.

  Here, the “polyester resin” widely means a resin of the system. Examples thereof include polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), and polytrimethylene terephthalate resin (PTT). The “main component” means that the material is contained in an amount of 50% by mass or more with respect to the entire layer including the material (hereinafter the same applies to the “main component”).

  The “tensile elongation at break” is determined based on JIS K7113. Further, the type of the resin having a tensile elongation at break of 10% or more is not particularly limited, and examples thereof include a resin mainly composed of urethane acrylate.

The invention according to claim 2 is characterized in that the pressure-sensitive adhesive layer of the optical sheet according to claim 1 has a function of blocking infrared rays, a function of blocking neon lines, a function of correcting color tone, a function of blocking ultraviolet rays, or an electromagnetic wave. It has one or a plurality of functions selected from the function of blocking.

The invention according to claim 3 is a polyester-based material on the surface opposite to the surface on which the base material layer (13) of the optical function sheet layer (14) of the optical sheet according to claim 1 or 2 is disposed. Another base material layer (23) mainly composed of a resin is provided.

Invention of Claim 4 contains the light absorption particle | grains whose average particle diameter is 1 micrometer or more in the light absorption part (16,16, ...) of the optical sheet as described in any one of Claims 1-3. It is characterized by.

  Here, “1 μm” when “the average particle diameter is 1 μm or more” is a value obtained by particle size measurement by a weight distribution method.

As for invention of Claim 5 , the prism part (15,15, ...) of the optical sheet as described in any one of Claims 1-4 is formed with the material which is refractive index Np, and light absorption part (16 , 16,... Are formed of a material having a refractive index Nb, and the refractive index Np is greater than or equal to the refractive index Nb.

The invention according to claim 6 solves the above-mentioned problem by providing a plasma display panel comprising the optical sheet according to any one of claims 1 to 5 .

  According to the optical sheet of the present invention, it is possible to prevent the prism portion from being cracked during the entire handling of the optical sheet during transportation or cutting. In particular, the effect is remarkable in a scene where a force is applied in the direction in which the warp of the optical sheet is corrected and a scene where a force is applied in the cutting direction. Thereby, the yield rate in optical sheet manufacture can be improved. Further, since the frequency of cracking of the prism portion is reduced, reliability can be obtained from the viewpoint of quality.

  Such an operation and gain of the present invention will be made clear from the best mode for carrying out the invention described below.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  FIG. 1 is a diagram schematically showing a layer configuration of an optical sheet 10 of the present invention according to the first embodiment. The optical sheet 10 includes a separator 11, an adhesive layer 12, a PET film layer 13 as a substrate layer, an optical function sheet layer 14, and a protective film 17. Each layer will be described below.

  The separator 11 is a film that is arranged so that the pressure-sensitive adhesive layer 12 does not adhere to the other when the optical sheet 10 is handled. Therefore, a normal film used for such purpose can be used. The material is not particularly limited, and examples thereof include PET.

  The pressure-sensitive adhesive layer 12 is a layer in which a pressure-sensitive adhesive for adhering the optical sheet 10 to an image providing device or the like is disposed as will be described later. The material of the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer 12 is not particularly limited as long as it transmits light and can appropriately bond the optical sheet 10 to the other. Examples thereof include an acrylic copolymer, and the adhesive strength thereof is about several N / mm to 20 N / 25 mm.

  The pressure-sensitive adhesive layer 12 may have other functions as well as having adhesiveness as described above. Examples thereof include IR (infrared) cut, NIR cut, neon line cut, ultraviolet ray cut, color tone correction (coloring), electromagnetic wave cut (EMI) and the like. Here, as a method of cutting neon lines, for example, phthalocyanine or the like can be dispersed in an adhesive.

  The PET film layer 13 is a film layer serving as a base for forming the optical function sheet layer 14 and is formed mainly of PET. The PET film layer 13 only needs to contain PET as a main component, and may contain other resins. Various additives may be added in appropriate amounts. Examples of general additives include phenol-based antioxidants, lactone-based stabilizers, and the like.

  The Young's modulus of PET used in the present embodiment is approximately 4500 to 4800 MPa, although the details vary depending on the type and additives. Further, the tensile elongation at break is approximately 100%. In addition, the PET film layer 13 is configured to transmit light because it is necessary to appropriately transmit the image light to the viewer side.

  The thickness of the PET film layer 13 is not particularly limited, but is preferably in the range of 100 μm to 200 μm.

  The PET film layer 13 may also have other functions. Examples thereof include IR (infrared) cut, NIR cut, neon line cut, ultraviolet ray cut, color tone correction (coloring), electromagnetic wave cut (EMI) and the like. Here, as a method for cutting neon lines, for example, phthalocyanine or the like can be dispersed in PET.

  The optical functional sheet layer 14 has a triangular cross section disposed between prism portions 15, 15,... Having a substantially trapezoidal cross section in a cross section perpendicular to the sheet surface of the optical sheet 10, and the prism portions 15, 15,. Some light absorption parts 16, 16,... Are provided.

  The prism parts 15, 15,... Are elements having a substantially trapezoidal cross section arranged such that the upper base faces the protective film 17 side and the lower base faces the PET film layer 13 side. In addition, the prism portions 15, 15,... Are made of a light transmissive resin having a predetermined refractive index (Np). Although the material is not particularly limited, for example, a material mainly composed of urethane acrylate that is cured by ionizing radiation can be used. And the elongation at break of the material constituting the prism parts 15, 15,... Of the optical sheet 10 of the present invention is 10% or more when formed as the prism parts 15, 15,. . Further preferred tensile elongation at break is 14% or more.

  As described above, the material constituting the prism portions 15, 15,... Provided in the optical sheet 10 of the present invention has a higher tensile strength than the material constituting the conventional prism portion having an elongation at break of about 3%. It has an elongation at break. A method for obtaining such a high tensile elongation at break is not particularly limited. For example, in a conventional urethane acrylate resin, the crosslinking density of the resin can be decreased.

  The light absorbing portions 16, 16,... Are elements having a triangular cross section disposed between the prism portions 15, 15,. One side of the triangular section is arranged facing the protective film 17 side. At this time, the inclined surface of the triangular section has an angle of 0 to 10 degrees with respect to the normal line of the light exit surface of the optical function sheet layer 14. And this does not necessarily need to be constant, and may be a polygonal line as long as the angle is within the above range. In this case, although the light absorption part is not strictly a triangular cross section, it maintains a substantially triangular cross section.

  Further, the light absorbing parts 16, 16,... Are made of a predetermined material having the same or smaller refractive index (Nb) as the prism parts 15, 15,. Further, the tensile elongation at break of the light absorbing portions 16, 16,... Is not necessarily 10% or more, but is preferably 10% or more or the same as that of the prism portions 15, 15,.

  In this way, the refractive index (Np) of the prism parts 15, 15... And the refractive index (Nb) of the light absorbing parts 16, 16,. It is possible to appropriately reflect light at the interface between the light absorption parts 16, 16,... And the prism parts 15, 15,.

  Further, the light absorbing portions 16, 16,... May contain light-absorbing particles, or the light absorbing portions 16, 16,... May be colored with pigments or dyes. Thereby, the external light from an observer side can be absorbed appropriately. When particles having light absorption properties are contained, the particle size of the particles is preferably 1 μm or more. Although the said particle | grain will not be specifically limited if it has light absorptivity, It is preferable that it is black and a commercially available particle | grain can also be used for this.

  The optical function sheet layer 14 is formed on the PET film layer 13 as follows, for example. That is, first, a liquid material to be a prism portion is applied to one side of the PET film. Next, it is cured by irradiating with ultraviolet rays in a state where the material to be the prism portion is sandwiched between the roll mold for forming the prism portion shape and the PET film, thereby forming the prism portions 15, 15,.

  Then, squeeze a material in which black light-absorbing particles are dispersed in a transparent resin having a refractive index of Nb between the formed prism portions 15, 15,..., And then the light-absorbing particles are dispersed. The transparent resin thus formed is cured to form the light absorbing portions 16, 16,.

  The protective film 17 is a film arranged for the purpose of protecting the optical sheet 10 from dust and scratches, and is peeled off immediately before the optical sheet 10 is attached. The protective film 17 is not particularly limited as long as the purpose is achieved. An example of the material is polypropylene.

  With the optical sheet 10 as described above, for example, during transportation, even when a large number of optical sheets are stacked, the lens is unlikely to crack. Further, even when the optical sheet 10 is cut into a predetermined size, cracks are unlikely to occur particularly in the cut portion. In addition to this, in any scene where the optical sheet is handled, it is possible to suppress the occurrence of cracking against the applied external force. As a result, it is possible to improve the yield rate in the manufacturing process and improve the reliability of the product.

  Here, the optical sheet 10 as one embodiment is shown, but the form is not limited to this. For example, regarding the optical function sheet layer, the optical sheet of the present invention can be obtained even if the shape of the prism portion or the light absorbing portion is changed. For this purpose, light absorbing portions 16 ′, 16 ′,..., 16 ″, 16 ′, like optical sheets 10 ′, 10 ″ which are modified examples as shown in FIGS. ',... Can be a rectangle or a polygon.

  Furthermore, in the optical function sheet layer, the directions of the prism portion and the light absorbing portion may be opposite. That is, the upper base (short side bottom) of the substantially trapezoidal prism portion is the PET film layer side, and the direction of the light absorbing portion is also reversed accordingly.

  The material of the base material layer is not necessarily PET, and “polyester resin” such as polybutylene terephthalate resin (PBT) or polytrimethylene terephthalate (PTT) resin can be used. In the present embodiment, it has been described that a resin having PET as a main component is a preferable material from the viewpoint of mass productivity, price, availability, etc. in addition to performance.

  FIG. 3 is a diagram schematically illustrating a layer configuration of the optical sheet 20 according to the second embodiment. The optical sheet 20 further has a PET film layer 23 on the side surface opposite to the PET film layer 13 of the optical function sheet layer 14 of the optical sheet 10 of the first embodiment. That is, the PET film layer 23 is provided between the optical function sheet layer 14 and the protective film 17. Since the description of the PET film layer 13 is applicable to the PET film layer 23, it is omitted here.

  FIG. 4 is a diagram schematically illustrating a layer configuration of the optical sheet 30 according to the third embodiment. The optical sheet 30 has an adhesive layer 32 on the side surface opposite to the PET film layer 13 of the optical functional sheet layer 14 of the optical sheet 10 of the first embodiment. That is, the pressure-sensitive adhesive layer 32 is provided between the optical function sheet layer 14 and the protective film 17. The adhesive layer 32 is not described here because the description of the adhesive layer 12 described above is applicable.

  In the case of such a configuration, for example, the optical sheet 30 can be directly bonded to a light source or the like.

  In addition, the layer structure is not particularly limited as long as it has the above-described effects of the present invention. For this, for example, an adhesive layer may be further provided between the PET film layer 23 and the protective film 17 of the second embodiment. According to this, the effect of the optical sheet 20 and the optical sheet 30 can be acquired.

  Next, each scene where the optical sheet 10 is used will be described. FIG. 5 is a diagram schematically showing a partially enlarged cross section of a portion where the optical sheet 10 is provided in a scene where the optical sheet 10 is disposed on the plasma television 1. In FIG. 5, the right side of the drawing is the observer side. Here, when the optical sheet 10 is attached to a video device or the like, the separator 11 and the protective film 17 are peeled off (the same applies hereinafter).

  As shown in FIG. 5, the plasma television 1 includes a plasma display panel (hereinafter sometimes referred to as “PDP”) 51, an air layer 52, and an optical sheet 10 from the side opposite to the viewer side. , A glass layer 53, an infrared cut film layer 54, an electromagnetic wave shielding layer 55, and a film layer 56 for preventing reflection. Appropriate image light can be provided to the observer by transmitting image light from the PDP 51 through each layer.

  Specifically, in the plasma television 1, light (image light) from the PDP 51 provides an image or the like to an observer through an optical path as indicated by arrows A, B, and C in FIG. At this time, the optical sheet 10 can control the image light so that the light (image light) from the PDP 51 becomes appropriate and easy to be seen by the observer. Further, the contrast can be adjusted by absorbing a part of the external light. Accordingly, in this case, the contrast can be improved by the optical sheet 10.

  Although the case where the optical sheet 10 is applied is shown here, the optical sheets 20 and 30 may be used instead of the optical sheet 10. When the optical sheet 30 is used, the optical sheet 30 is directly bonded to the PDP 51 by the pressure-sensitive adhesive layer 32.

  Next, another scene where the optical sheet 10 is used will be described. FIG. 6 is a diagram schematically illustrating a layer configuration in a portion where the optical sheet 10 of the liquid crystal display device 2 using the optical sheet 10 is disposed. A configuration example is a transmissive liquid crystal display device. The liquid crystal display device 2 includes a planar light source 61 and a transmissive liquid crystal panel 62, and the optical sheet 10 is provided therebetween.

  The planar light source 61 is disposed on the back side of the liquid crystal panel 62, and the planar light source 61 serves as a backlight for the liquid crystal panel 62. The planar light from the planar light source 61 is emitted toward the back surface of the liquid crystal panel 62 through the optical sheet 10. At this time, optical paths such as arrows D, E and F are taken. That is, at this time, the optical sheet 10 is incident on the back surface of the liquid crystal panel 62 by controlling the light output angle so that the planar light does not spread greatly. Thereby, an image is displayed on the liquid crystal panel 62.

  As described above, in the liquid crystal display device 2, the optical sheet 10 can control the viewing angle. The optical sheet of the present invention can also be applied to an optical sheet having such a viewing angle control function. In FIG. 6, the optical sheet 10 is disposed on the surface light source 61 side of the liquid crystal panel 62. However, the optical sheet 10 is not limited to this position, and may be attached to the viewer side, for example. As a result, a sheet having a viewing angle control function can be optionally provided later according to the user's intention.

  Although the case where the optical sheet 10 is applied is shown here, the optical sheets 20 and 30 may be used instead of the optical sheet 10. Further, the optical sheets 10, 20, and 30 may be provided on one surface thereof with the above-described infrared cut film layer, electromagnetic wave shield layer, film layer for preventing reflection, and the like.

  Furthermore, another scene where the optical sheet 10 is used will be described. FIG. 7 is a diagram schematically showing a layer configuration in a portion where the optical sheet 10 of the projection screen 3 using the optical sheet 10 is disposed. In the projection screen 3, it is arranged such that the lower base of the prism sections 15, 15,. The projection screen 3 includes a Fresnel lens layer 71, the optical sheet 10, and a diffusion sheet layer 72 from the light source side. Here, the diffusion sheet is a sheet having a function of diffusing light.

  Light from the light source passes through the Fresnel lens layer 71 along a predetermined optical path, further passes through the diffusion sheet layer 72 via the optical sheet 10, and reaches the observer. At this time, optical paths such as arrows G, H and I are taken. That is, the optical sheet 10 emits light to the observer side so as to diffuse by controlling the angle of incident light.

  As described above, in the projection screen 3, the optical sheet 10 can diffuse light. The optical sheet of the present invention can also be applied to an optical sheet having such a light diffusion function.

  Although the case where the optical sheet 10 is applied is shown here, the optical sheets 20 and 30 may be used instead of the optical sheet 10. Further, the optical sheets 10, 20, and 30 may be provided on one surface thereof with the above-described infrared cut film layer, electromagnetic wave shield layer, film layer for preventing reflection, and the like.

  Examples of the optical sheet having the above configuration will be described below in more detail. However, the present invention is not limited to the scope of the examples.

As an example, the bending test for obtaining the tensile elongation at break specified in JIS-K7113 was performed on the optical sheet of the present invention and the conventional optical sheet. The conditions are shown below.
<Test conditions>
-Atmospheric temperature and humidity: 23 ° C, 55%
<Specimen>
・ Size: No. 1 1/2 dumbbell (JIS-K7113)
・ Marking distance: 50mm
Deformation speed: 10 mm / min. Tensile elongation at break: 3.4% (conventional example), 14.5%, 29.5%, 45.6%

<Evaluation method>
Based on the above test, a bending test is performed.
・ If cracks are applied intentionally, cracking occurs: △
-Cracks generated during normal transportation (transported with 200 sheets loaded): ×

<Result>
Table 1 shows the results.

  As can be seen from Table 1, by increasing the tensile elongation at break, the occurrence of cracks due to bending can be suppressed. If the tensile elongation at break is set to 10% or more as compared with the conventional case, it is possible to sufficiently prevent the occurrence of cracking which has been a problem until now. Further, in the case of 10% or more, the effect becomes even more remarkable if the tensile elongation at break is larger.

  Although the present invention has been described with reference to the most practical and preferred embodiments at the present time, the invention is limited to the embodiments disclosed herein. However, the invention can be changed as appropriate without departing from the scope or spirit of the invention that can be read from the claims and the entire specification, and optical sheets and the like accompanying such changes are also included in the technical scope of the present invention. Must be understood.

It is a figure showing the section of the optical sheet of the present invention concerning a first embodiment, and showing the layer composition typically. It is the figure which represented typically the layer structure of the modification of the optical sheet of this invention. It is a figure showing the section of the optical sheet of the present invention concerning a second embodiment, and showing the layer composition typically. It is a figure showing the section of the optical sheet of the present invention concerning a third embodiment, and showing the layer composition typically. It is a figure which shows the example in which the optical sheet and optical film of this invention were used for the plasma television. It is a figure which shows the example in which the optical sheet of this invention was used for the liquid crystal display device. It is a figure which shows the example in which the optical sheet of this invention was used for the projection screen. It is a figure which shows an example of the conventional optical sheet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plasma television 2 Liquid crystal display device 3 Projection screen 10 Optical sheet 11 Separator 12 Adhesive layer 13 PET film layer (base material layer)
14 Optical function sheet layer 15 Prism part 16 Light absorption part 17 Protective film 20 Optical sheet 30 Optical sheet

Claims (6)

  An optical sheet comprising a layer that controls and emits incident light,
  A base material layer mainly composed of a polyester-based resin;
In the cross section that is laminated on one surface of the base material layer and is orthogonal to the light incident surface, prism portions that can transmit light and light absorption portions that can absorb light are alternately arranged along the sheet surface. An optical function sheet layer,
An adhesive layer disposed on the light incident side and / or the light outgoing side, and
  The optical sheet, wherein the prism portion of the optical function sheet layer is made of a resin having a tensile breaking elongation of 14.5% or more and 45.6% or less. The adhesive layer has one or more functions selected from a function of blocking infrared rays, a function of blocking neon lines, a function of correcting color tone, a function of blocking ultraviolet rays, and a function of blocking electromagnetic waves. The optical sheet according to claim 1 . Claim 1 or 2, characterized in that the said surface of the substrate layer is disposed in the optical functional sheet layer to a surface opposite to another substrate layer mainly composed of polyester resin is provided The optical sheet according to 1. The optical sheet according to any one of claims 1 to 3, an average particle diameter in the light absorbing portion is characterized by containing the above light-absorbing particles 1 [mu] m. The prism portion is formed of a material having a refractive index Np, the light absorption portion is formed of a material having a refractive index Nb, and the refractive index Np is greater than or equal to the refractive index Nb. The optical sheet according to any one of claims 1 to 4 , wherein: A plasma display panel comprising the optical sheet according to any one of claims 1 to 5 .

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