JP5041784B2 - Backlight unit - Google Patents

Description

  The present invention relates to a backlight unit that is used in a display such as a liquid crystal display device, a display device, an illumination device, and the like, and includes a linear light source and an optical functional sheet having both a light collecting function and a light diffusion function. .

In recent years, a lens film for condensing light from a light source such as a light guide plate in the front direction, a diffusion sheet for diffusing, and the like have been used for applications such as liquid crystal display elements and organic EL displays.
For example, in a direct type backlight used in a television or the like as shown in FIG. 13, light emitted from a light source 92 such as a light guide plate is incident on a condensing film (optical functional sheet) 91 and is incident on the incident light. The part is refracted and transmitted by the optical functional sheet 91, the angle of emission is changed and emitted in the front direction, and the rest is reflected and returned to the light source 92. The reflected light from the optical functional sheet 91 is reflected by the surfaces of the light source 92, the diffusing plate 93, the diffusing sheet 94, etc., and is incident on the condensing film again.
With such a configuration, the luminance distribution of the emitted light from the light source is widely dispersed and the front luminance is lowered. Therefore, the optical functional sheet 91 reduces the luminance from the light source in the front direction. The directional characteristics have been improved to be higher.

  In order to improve the light diffusion function of the optical functional sheet 91 used in the backlight unit, there is one in which the surface shape of the prism structure is changed in accordance with the pitch period of the linear light source. Here, if the light diffusion function of the optical functional sheet 91 is improved, the light condensing function is lowered. Therefore, in order to achieve both the light diffusion function and the light condensing function, the apex (vertical angle) of the prism structure is slightly adjusted. The shape of the prism structure was partially changed.

  Specifically, although the linear light source unevenness is reduced by changing the shape of the fine prism structure of the optical functional sheet and the arrangement pitch of the linear light sources (see, for example, Patent Document 1), There is a problem that the front luminance is reduced, it is necessary to make a mold for each arrangement pitch of the linear light sources, and alignment is essential.

  In addition, although the linear light source unevenness is prevented by changing the shape of the prism structure based on the arrangement pitch period of the linear light sources (see, for example, Patent Document 2), in this case, the front luminance decreases. There is a problem that alignment is essential.

  In addition, the apex angle of the prism structure is set to 40 to 80 °, the light emitted from the position immediately below the linear light source is diffused to remove the linear light source unevenness, and the side lobe due to the reduced apex angle of the prism structure. Is increased by making the apex of the prism structure a curved surface (providing R at the apex) (see, for example, Patent Document 3), but the light collecting function is reduced although alignment is unnecessary. There's a problem. Here, the light collecting sheet is intended to collect light on the front of the display, but depending on the shape, a phenomenon in which a luminance peak appears in an oblique (about 70 °) direction as well as the front (0 °) is called a side lobe.

  Also, a prism having a V-groove formed on the surface of the light diffusing plate is molded, and the apex angle of the prism structure that can obtain high diffusibility by the linear light source pitch and the distance between the light diffusing plate and the linear light source Is calculated (for example, see Patent Document 4), but there is a problem that the light collecting function is lowered. In addition, the diffusivity is improved by rotating the prism in which the V-groove is formed by 60 ° or less with respect to the linear light source (by increasing the cross-sectional apex angle of the prism structure). Because of the change, there is a problem that the line light source unevenness becomes more conspicuous from other than the front, and the yield of the product decreases as the rotation increases.

JP-A-6-308485 JP 2002-352611 A JP 2006-140124 A JP 2006-195276 A

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, the present invention provides a backlight unit capable of improving the light diffusing function and reducing the linear light source unevenness without deteriorating the light collecting function, generating side lobes, and reducing productivity. The purpose is to do.

Means for solving the problems are as follows. That is,
<1> A backlight unit comprising an optical functional sheet in which a prism structure having a plurality of prism bodies is formed on at least one surface, and a plurality of linear light sources arranged in parallel to the optical functional sheet. In the luminance distribution diagram showing the luminance distribution in the optical functional sheet, the maximum luminance at the center of the backlight unit in the optical functional sheet is B _max , the minimum luminance is B _min , and the plurality of lines The peak position of the first virtual image among the plurality of virtual images expressed from the shaped light source is A ₁ , the peak height is H _1, and the peak position of the second virtual image adjacent to the first virtual image is A ₂ , the peak The height is H ₂ ,..., The peak position of the (n−1) th virtual image adjacent to the (n−2) th virtual image is A _n−1 , the peak height is H _n−1, and the n−1 th Next to the virtual image If the peak position of the virtual image of the n and _{A n,} the peak height and _{H n,} so that the value is substantially constant _{(H n-1 + H n} ) / (A n -A n-1), the line A distance d between the light source and the optical functional sheet is selected, and the distance d is
(1) In the case where the shape of the prism body is a substantially quadrangular pyramid, the arrangement direction of the prism bodies is parallel to the alignment direction of the linear light source, and the virtual image corresponds to one linear light source. When three are expressed, it is calculated by the following formula (1-1) or the following formula (1-2),
(2) When the shape of the prism bodies is a regular quadrangular pyramid, the arrangement direction of the prism bodies is inclined by an angle X ° with respect to the orientation direction of the linear light sources so as to reduce luminance unevenness, and the linear light sources When four virtual images are expressed for one, it is calculated by the following formula (1-3) or the following formula (1-4),
(3) The prism body has a V-groove shape and one optical functional sheet, and the arrangement direction of the prism bodies is parallel to the alignment direction of the linear light source, and the linear light source When two virtual images are expressed for one, it is calculated by the following formula (1-5) or the following formula (1-6),
(4) In the case where the prism body has a V-groove shape and two optical functional sheets, the angle X at which the arrangement direction of the prism bodies can reduce luminance unevenness with respect to the alignment direction of the linear light source The back is calculated by the following formula (1-7) or the following formula (1-8) when tilted and four virtual images are expressed for one linear light source. It is a light unit.
However, refers to the maximum value of the peak and the peak height _{H n,} the peak height _{H n} from the virtual points to satisfy peak of _{H n ≧ 0.3 × (B max} -B min), the The peak position refers to the position where the peak appears on the horizontal axis indicating the arrangement direction of the plurality of linear light sources in the luminance distribution diagram, and the central part of the backlight unit is the number of the plurality of linear light sources. N (even) lines, the leftmost linear light source being the first linear light source, the linear light source adjacent to the first linear light source being the second linear light source, ... (N-2) line When the linear light source adjacent to the linear light source is the (N-1) th linear light source and the linear light source adjacent to the (N-1) th linear light source is the Nth linear light source, (N / 2) -1) refers to a region including three linear light sources, a linear light source, a (N / 2) th linear light source, and a (N / 2 + 1) th linear light source, The degree distribution diagram shows the luminance distribution in the optical functional sheet when the backlight unit does not include a diffusion sheet and a diffusion plate.
In addition, the formulas (1-1) to (1-8) are expressed by the refractive index “n ′” of the optical functional sheet and the slope angle “θ” of the light exit surface of the light emitted from the linear light source in the prism body. And a line of intersection between a plane that includes one linear light source of the plurality of linear light sources and that is orthogonal to the optical functional sheet and a plane that includes the optical functional sheet, and the one linear It is calculated based on the pitch “p” of the linear light source, which is the distance from the virtual image closest to the intersecting line excluding the intersecting virtual image among the virtual images in the optical functional sheet expressed from the light source.
In <1>, the distance d between the linear light source and the optical functional sheet is such that the value of (H _n-1 + H _n ) / (A _n -A _n-1 ) is substantially constant. Since it is selected, the light diffusion function can be improved and the linear light source unevenness can be reduced without reducing the light collecting function.
<2> A sum of a peak height of one virtual image of a plurality of virtual images expressed from a plurality of linear light sources, a peak height of a virtual image adjacent to the one virtual image, and a peak position interval of the adjacent virtual images The backlight unit according to <1>, wherein the ratio is substantially equal.
<3> A backlight unit comprising an optical functional sheet in which a prism structure having a plurality of prism bodies is formed on at least one surface, and a plurality of linear light sources arranged in parallel to the optical functional sheet. And the linear light source so that the brightness of the virtual image in the optical functional sheet expressed from the plurality of linear light sources is substantially equal, and the distance between adjacent virtual images in the optical functional sheet is substantially equal. A distance d to the optical functional sheet is selected, and the distance d is
(1) In the case where the shape of the prism body is a substantially quadrangular pyramid, the arrangement direction of the prism bodies is parallel to the alignment direction of the linear light source, and the virtual image corresponds to one linear light source. When three are expressed, it is calculated by the following formula (1-1) or the following formula (1-2),
(2) When the shape of the prism bodies is a regular quadrangular pyramid, the arrangement direction of the prism bodies is inclined by an angle X ° with respect to the orientation direction of the linear light sources so as to reduce luminance unevenness, and the linear light sources When four virtual images are expressed for one, it is calculated by the following formula (1-3) or the following formula (1-4),
(3) The prism body has a V-groove shape and one optical functional sheet, and the arrangement direction of the prism bodies is parallel to the alignment direction of the linear light source, and the linear light source When two virtual images are expressed for one, it is calculated by the following formula (1-5) or the following formula (1-6),
(4) In the case where the prism body has a V-groove shape and two optical functional sheets, the angle X at which the arrangement direction of the prism bodies can reduce luminance unevenness with respect to the alignment direction of the linear light source The back is calculated by the following formula (1-7) or the following formula (1-8) when tilted and four virtual images are expressed for one linear light source. It is a light unit.
However, the formulas (1-1) to (1-8) are expressed by the refractive index “n ′” of the optical functional sheet and the slope angle “θ” of the light exit surface of the light emitted from the linear light source in the prism body. And a line of intersection between a plane that includes one linear light source of the plurality of linear light sources and that is orthogonal to the optical functional sheet and a plane that includes the optical functional sheet, and the one linear It is calculated based on the pitch “p” of the linear light source, which is the distance from the virtual image closest to the intersecting line except the virtual image on the intersecting line among the virtual images in the optical functional sheet expressed from the light source.
In <3>, the linear light source is such that the brightness of the virtual image in the optical functional sheet expressed from the plurality of linear light sources is substantially equal, and the distance between adjacent virtual images in the optical functional sheet is substantially equal. Since the distance d between the optical functional sheet and the optical functional sheet is selected, the light diffusion function can be improved and the linear light source unevenness can be reduced without deteriorating the light collecting function.
<4> When the region from the plurality of linear light sources to the other linear light sources adjacent to the linear light source and the region on the emission side toward the optical functional sheet in the region are defined as the region R, A region from a first linear light source to a second linear light source adjacent to the first linear light source among a plurality of linear light sources, and a region on the emission side toward the optical functional sheet in the region A region R ₁ , a region from the second linear light source to a third linear light source adjacent to the second linear light source, and an exit side region toward the optical functional sheet of the region, Region R ₂ ,... Region from the (n−1) -th linear light source to the n-th linear light source adjacent to the n-th linear light source, and the emission side of the region toward the optical functional sheet region R _n-1 and an area of _a region up to the (n + 1) of the linear light source which is adjacent to the linear light sources of the n-th from the linear light source of the n, the region An exit side of the area towards the optical functional sheet when a region R _n, the average value of the luminance of the optical functional sheet in the region R _n, the luminance of the optical functional sheet in the region R _n The backlight unit according to <3> , wherein a value obtained by dividing a standard deviation (luminance standard deviation / luminance average value) is 0.540 or less.
<5> The prism body has two first exit surfaces facing each other and two second exit surfaces facing each other, and the sum of the areas of the two first exit surfaces is The backlight unit according to any one of <1> to <4>, wherein the backlight unit is a substantially quadrangular pyramid substantially equal to one area of the second emission surface.

  According to the present invention, the above-described problems can be solved, and the light diffusion function can be improved and the linear light source unevenness can be reduced without lowering the light collecting function, generating side lobes, lowering productivity, etc. A backlight unit that can be provided can be provided. Further, when the backlight unit is used in a liquid crystal display device, moire with liquid crystal pixels can be prevented.

(Backlight unit)
The backlight unit of the present invention includes a linear light source, an optical functional sheet, and other members.

<Linear light source>
As the linear light source, a cold cathode tube, a hot cathode tube, a linearly arranged LED, a combination of an LED and a light guide, and the like can be used. At this time, the cold-cathode tube or the hot-cathode tube has a shape similar to U, in which two parallel tubes are connected by a single semi-circle, in addition to a straight line, and three parallel tubes Use a shape similar to N, which is connected by two approximately semicircles, or a shape similar to W, where four parallel pipes are connected by three approximately semicircles. be able to.
The linear light source is preferably a cold cathode tube from the viewpoint of luminance uniformity, and a combination of LEDs and light guides arranged in a linear form from the viewpoint of luminous efficiency.

<Optical functional sheet>
FIG. 1 is a perspective view showing a partial configuration of the optical functional sheet of the present invention. As shown in FIG. 1, the optical functional sheet 1 of the present invention includes at least a base material 3 on which a prism body 4 described later is formed, and has a support body 2 that supports the base material 3 as necessary. Here, the support body 2 and the base material 3 may be formed of a single resin.
The base material 3 includes an incident surface 3b (hereinafter also referred to as a reference surface 3b) on which light emitted from a light source such as a backlight is incident through the support 2, and an opposite side of the incident surface 3b. A plurality of prism bodies 4 for condensing light in a predetermined direction have a prism body forming surface 3a formed on substantially the entire surface.
As a form of such an optical functional sheet 1, for example, a prism sheet and a lenticular lens are typical, and a diffraction grating and the like are also included in addition to these.
In addition, the optical functional sheet 1 of this invention may have other layers, such as a light-diffusion layer, a back layer, and an intermediate | middle layer, as needed.

<< Support >>
There is no restriction | limiting in particular as a shape of the support body 2, According to the objective, it can select suitably, For example, rectangular shape, square shape, circular shape etc. are mentioned.
There is no restriction | limiting in particular as a structure of the support body 2, According to the objective, it can select suitably, For example, a single layer, a multilayer, etc. are mentioned.
There is no restriction | limiting in particular as a magnitude | size of the support body 2, According to the objective, it can select suitably.

  The material of the support (sheet) 2 is not particularly limited as long as it is transparent and has a certain strength. For example, resin film, paper (resin coated paper, synthetic paper, etc.), metal foil (Aluminum web etc.) etc. can be used. As the material of the resin fill, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyester, polyolefin, acrylic, polystyrene, polycarbonate, polyamide, PET (polyethylene terephthalate), biaxially stretched polyethylene terephthalate, Known materials such as polyethylene naphthalate, polyamideimide, polyimide, aromatic polyamide, cellulose acylate, cellulose triacetate, cellulose acetate propionate, and cellulose diacetate can be used. Of these, polyester, cellulose acylate, acrylic, polycarbonate, and polyolefin can be preferably used.

As the width of the support 2, 0.1 to 3 m is generally employed, and as the length of the support 2, 1,000 to 100,000 m is generally employed. Is generally 1 to 300 μm. However, application of other sizes is not precluded.
The thickness of the support 2 is, for example, a film thickness meter that measures the thickness of the support 2 by sandwiching the support 2 with a measuring meter, or a non-contact film thickness that measures the thickness of the support 2 using optical interference. It can be measured by using a meter or the like.

  These supports 2 may be previously subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment and the like. The surface roughness Ra of the support 2 is preferably 3 to 10 nm at a cutoff value of 0.25 mm.

  In addition, the support 2 may be a substrate in which an underlayer such as an adhesive layer is provided in advance and dried and cured, or a substrate in which another functional layer is formed in advance on the back surface. Similarly, the support 2 may have not only a single layer structure but also a structure having two or more layers.

Further, the haze of the support 2 is 50% or less, preferably 40% or less, more preferably 30% or less, and still more preferably 20% or less. When the haze exceeds 50%, the light collection efficiency may be significantly reduced.
Here, the “haze” refers to a value of the degree of cloudiness, and is a value evaluated by a measuring device such as a haze meter (model number: HZ-1, manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS 7105, for example. is there.

<< Optical Functional Sheet Manufacturing Apparatus and Manufacturing Method >>
The manufacturing apparatus and manufacturing method used for manufacturing the optical functional sheet are not particularly limited as long as a fine uneven shape can be formed. For example, the manufacturing apparatus 20 having the configuration shown in FIG. 2 was used. The method is preferably used.
The manufacturing apparatus 20 includes a sheet supply unit 21, a coating unit 22, a drying unit 29, an embossing roll 23 that is an uneven roll, a nip roll 24, a resin curing unit 25, a peeling roll 26, a protective film supply unit 27, and a sheet winding unit 28. It is composed of

  The sheet supply means 21 is for feeding a sheet, and is composed of a feed roll around which the sheet is wound.

  The coating means 22 is a device that applies a radiation curable resin to the surface of the sheet. The supply means 22A for supplying the radiation curable resin, a supply device (pump) 22B, a coating head 22C, and a sheet are wound at the time of coating. The supporting roller 22D is hung and supported, and a pipe for supplying the radiation curable resin supply source 22A to the coating head 22C. In FIG. 4, an application head of an extrusion type die coater is used as the coating head.

  As the drying means 29, as long as the coating liquid applied to the sheet can be uniformly dried as in the tunnel-shaped drying apparatus shown in FIG. Can be used. Specific examples include a radiant heating system using a heater, a hot air circulation system, a far infrared system, and a vacuum system.

  The embossing roll 23 is required to have a concavo-convex pattern accuracy, mechanical strength, roundness, and the like so that the ruggedness of the roll surface can be transferred and formed on the surface of the sheet. As such an embossing roll 23, a metal roll is preferable, for example.

  A regular fine uneven pattern is formed on the outer peripheral surface of the embossing roll 23. Such a regular fine concavo-convex pattern is required to have a shape obtained by inverting the fine concavo-convex pattern on the surface of an embossed sheet as a product.

  As an embossed sheet as a product, for example, a lens in which fine concavo-convex patterns such as lenticular lenses and prism lenses are arranged two-dimensionally; for example, a lens in which fine concavo-convex patterns such as fly-eye lenses are arranged three-dimensionally; A flat lens or the like in which fine cones are laid in the X and Y directions is an object, and a regular fine uneven pattern on the outer peripheral surface of the embossing roll 23 corresponds to these lenses.

  As a method of forming a regular fine uneven pattern on the outer peripheral surface of the embossing roll 23, for example, a method of cutting the surface of the embossing roll 23 with a diamond bit (single point); Examples thereof include a method of directly forming irregularities by drawing, laser processing, and the like. Further, unevenness is formed on the surface of the thin metal plate by photo etching, electron beam drawing, laser processing, optical modeling, etc., and this plate is wound around the roll and fixed, The method of doing is also mentioned. In addition, uneven surfaces are formed on the surface of materials that are easier to process than metal by photoetching, electron beam drawing, laser processing, stereolithography, etc. There is also a method in which a plate-shaped body made is manufactured, and this plate-shaped body is wound and fixed around the roll to form an emboss roll 23. In particular, when the reversal mold is formed by electroforming or the like, there is a feature that a plurality of plate-like bodies having the same shape can be obtained from one original plate (mother).

It is preferable to perform a mold release process on the surface of the embossing roll 23. Thus, the shape of the fine concavo-convex pattern can be satisfactorily maintained by performing the mold release process on the surface of the embossing roll 23.
As the mold release treatment, various known methods can be appropriately selected according to the purpose, and examples thereof include a coating treatment with a fluororesin. The embossing roll 23 is preferably provided with driving means. Further, the embossing roll 23 rotates counterclockwise (CCW) as shown by the arrow in the figure.

  The nip roll 24 forms a roll while pressing the sheet while being paired with the embossing roll 23, and is required to have predetermined mechanical strength, roundness, and the like. The longitudinal elastic modulus (Young's modulus) of the surface of the nip roll 24 is set to an appropriate value because roll forming is insufficient if it is too small, and if it is too large, it reacts sensitively to the inclusion of foreign substances such as dust and tends to cause defects. It is preferable. The nip roll 24 is preferably provided with a driving means. Further, the nip roll 24 rotates in the clockwise direction (CW) as shown in the figure.

  In order to apply a predetermined pressing force between the embossing roll 23 and the nip roll 24, it is preferable to provide a pressing means on either the embossing roll 23 or the nip roll 24. Similarly, it is preferable to provide fine adjustment means on either the embossing roll 23 or the nip roll 24 so that the clearance (clearance) or pressure between the embossing roll 23 and the nip roll 24 can be accurately controlled.

  The resin curing means 25 is a radiation irradiation means provided opposite to the embossing roll 23 on the downstream side of the nip roll 24. This resin curing means 25 transmits the sheet by radiation irradiation and cures the resin layer, and can preferably irradiate the radiation according to the curing characteristics of the resin and irradiate the amount of radiation according to the sheet conveyance speed. . As the resin curing means 25, for example, a cylindrical irradiation lamp having substantially the same length as the width of the sheet can be mentioned. A plurality of the cylindrical irradiation lamps may be provided in parallel, or a reflection plate may be further provided on the back surface of the cylindrical lamp.

The peeling roll 26 is a pair of the embossing roll 23 and peels the sheet from the embossing roll 23, and is required to have predetermined mechanical strength, roundness, and the like.
Specifically, the sheet is peeled from the embossing roll 23 while being sandwiched between the rotating embossing roll 23 and the peeling roll 26 at the peeling location, and the sheet is wound on the peeling roll 26. Wrap it around. In order to ensure this operation, the peeling roll 26 is preferably provided with a driving means. The peeling roll 26 rotates clockwise (CW).

  Moreover, when the temperature of resin etc. rises by hardening, you may provide a cooling means in the peeling roll 26 in order to cool a sheet | seat at the time of peeling, and to ensure peeling.

  In addition, although illustration was abbreviate | omitted, between the pressing location (9 o'clock position) of the embossing roll 23 and the peeling location (3 o'clock position), a plurality of backup rolls are provided to face each other. The curing process may be performed while pressing the sheet with the roll 23.

  The sheet take-up means 28 stores the peeled sheet, and includes a take-up roll that takes up the sheet. By the sheet winding means 28, the protective film supplied from the adjacent protective film supply means 27 is supplied to the surface of the sheet, and is stored in the sheet winding means 28 in a state where both films are overlapped.

  Further, in the manufacturing apparatus 20, a guide roller or the like that forms a sheet conveyance path may be provided between the coating unit 22 and the embossing roll 23, between the peeling roll 26 and the sheet winding unit 28, and the like. In addition, a tension roller or the like may be provided as needed to absorb slack during conveyance of the sheet W.

  Next, the operation of the manufacturing apparatus 20 will be described. The sheet is fed from the sheet supply means 21 at a constant speed. The sheet is fed into the application means 22 and the resin is applied to the surface of the sheet. After application, the solvent in the coating solution is evaporated by the drying means 29. Next, the sheet is fed into forming means composed of an embossing roll 23 and a nip roll 24. Thus, roll forming is performed while pressing the continuously running sheet with the rotating embossing roll 23 and the nip roll 24 at the 9 o'clock position of the embossing roll 23. That is, the sheet is wound around the rotating embossing roll 23, and the unevenness on the surface of the embossing roll 23 is transferred to the resin layer.

  Next, in a state where the sheet is wound around the embossing roll 23, the resin curing means 25 transmits the sheet and irradiates the resin layer with radiation, thereby curing the resin layer. Then, the sheet is peeled from the embossing roll 23 by winding the sheet around the peeling roll 26 at the 3 o'clock position of the embossing roll 23.

  In addition, although not shown in FIG. 2, after peeling a sheet | seat, in order to further accelerate hardening, you may irradiate again.

  The peeled sheet is conveyed to the sheet take-up means 28, the protective film supplied from the protective film supply means 27 is supplied to the surface of the sheet, and the take-up roll of the sheet take-up means 28 in a state where both films overlap. Is wound and stored.

  Thus, the resin layer is formed on the surface of the sheet without unevenness of thickness, and the embossing roll is also stably and uniformly pressed. Thereby, the uneven | corrugated sheet | seat in which the regular fine uneven | corrugated pattern was formed in the surface can be manufactured with high quality without a defect.

  Further, in the example of the manufacturing apparatus 20 described above, the embodiment in which the roll-shaped embossing roll 23 is used has been described. However, the surface of the belt such as an endless belt having an uneven pattern (embossed shape) is used. Also good. This is because even such a belt acts in the same manner as a cylindrical roll, and the same effect can be obtained.

<< Material of optical functional sheet >>
Examples of the material of the sheet used as the optical functional sheet include a resin film, paper (resin coated paper, synthetic paper, etc.), metal foil (aluminum web, etc.), and the like.
Examples of the material of the resin film include polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyester, polyolefin, acrylic, polystyrene, polycarbonate, polyamide, PET (polyethylene terephthalate), and biaxial stretching. Examples include polyethylene terephthalate, polyethylene naphthalate, polyamideimide, polyimide, aromatic polyamide, cellulose acylate, cellulose triacetate, cellulose acetate propionate, and cellulose diacetate. Of these, polyester, cellulose acylate, acrylic, polycarbonate, and polyolefin are particularly preferably used.

  The sheet generally has a width of 0.1 to 3 m, a length of 1,000 to 100,000 m, and a thickness of 1 to 300 μm. However, application of other sizes is not impeded.

  The sheet may be previously subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment, and the like. The surface roughness Ra of the sheet is preferably 3 to 10 nm at a cutoff value of 0.25 mm.

  In addition, the sheet may be a sheet provided with a base layer such as an adhesive layer in advance and dried and cured, or a sheet in which another functional layer is previously formed on the back surface. Similarly, as the sheet, not only one having a single layer structure but also one having two or more layers may be used. Moreover, it is preferable that the said sheet | seat is a transparent body and anti-transparent body which can permeate | transmit light.

As the resin used for the resin layer, for example, a reactive group-containing compound such as a (meth) acryloyl group, a vinyl group, and an epoxy group can be reacted with the reactive group-containing compound by irradiation with ultraviolet rays or the like. And compounds containing compounds that generate active species such as radicals and cations.
In particular, from the viewpoint of curing speed, a combination of a reactive group-containing compound (monomer) containing an unsaturated group such as a (meth) acryloyl group or a vinyl group and a photo radical polymerization initiator that generates a radical by light is preferable. . Among these, (meth) acryloyl group-containing compounds such as (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, and polyester (meth) acrylate are preferable. As this (meth) acryloyl group-containing compound, a compound containing one or more (meth) acryloyl groups can be used. Moreover, the reactive group containing compound (monomer) containing unsaturated groups, such as said acryloyl group and a vinyl group, may be used individually by 1 type, and 2 or more types are mixed and used as needed. May be.

  Examples of the (meth) acryloyl group-containing compound include, for example, isobornyl (meth) acrylate, bornyl (meth) acrylate, and tricyclodecanyl (meth) as monofunctional monomers containing only one (meth) acryloyl group-containing compound. Acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 4-butylcyclohexyl (meth) acrylate, acryloylmorpholine, 2-hydroxyethyl (meth) Acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (Meth) acrylate, butyl (meth) acrylate, amyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, Heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, Dodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, butto Siethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, methoxyethylene glycol (meth) acrylate, ethoxyethyl (meth) acrylate, methoxypolyethylene glycol (meth) Examples include acrylate and methoxypolypropylene glycol (meth) acrylate.

Moreover, as a monofunctional monomer having an aromatic ring, phenoxyethyl (meth) acrylate, phenoxy-2-methylethyl (meth) acrylate, phenoxyethoxyethyl (meth) acrylate, 3-phenoxy-2-hydroxypropyl (meth) acrylate, 2-phenylphenoxyethyl (meth) acrylate, 4-phenylphenoxyethyl (meth) acrylate, 3- (2-phenylphenyl) -2-hydroxypropyl (meth) acrylate, and p-cumylphenol reacted with ethylene oxide ( (Meth) acrylate, 2-bromophenoxyethyl (meth) acrylate, 4-bromophenoxyethyl (meth) acrylate, 2,4-dibromophenoxyethyl (meth) acrylate, 2,6-dibromophenoxyethyl ( Data) acrylate, 2,4,6-bromophenyl (meth) acrylate, 2,4,6-tribromophenoxyethyl (meth) acrylate.
Examples of commercially available monofunctional monomers having an aromatic ring include, for example, Aronix M113, M110, M101, M102, M5700, TO-1317 (above, manufactured by Toagosei Co., Ltd.), Biscote # 192, # 193. # 220, 3BM (Osaka Organic Chemical Co., Ltd.), NK Ester AMP-10G, AMP-20G (Established, Shin-Nakamura Chemical Co., Ltd.), Light Acrylate PO-A, P-200A, Epoxy ester M-600A, light ester PO (above, manufactured by Kyoeisha Chemical Co., Ltd.), New Frontier PHE, CEA, PHE-2, BR-30, BR-31, BR-31M, BR-32 (above, first Kogyo Seiyaku Co., Ltd.).

  Examples of unsaturated monomers having two (meth) acryloyl groups in the molecule include alkyl diols such as 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, and 1,9-nonanediol diacrylate. Diacrylate; polyalkylene glycol diacrylate such as ethylene glycol di (meth) acrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate; neopentyl glycol di (meth) acrylate, tricyclodecane methanol diacrylate, and the like.

Examples of unsaturated monomers having a bisphenol skeleton include ethylene oxide-added bisphenol A (meth) acrylate, ethylene oxide-added tetrabromobisphenol A (meth) acrylate, propylene oxide-added bisphenol A (meth) acrylate, propylene oxide Addition tetrabromobisphenol A (meth) acrylic acid ester, bisphenol A epoxy (meth) acrylate obtained by epoxy ring-opening reaction of bisphenol A diglycidyl ether and (meth) acrylic acid, tetrabromobisphenol A diglycidyl ether and (meth ) Tetrabromobisphenol A epoxy (meth) acrylate, bisphenol F diglycidyl ether obtained by epoxy ring-opening reaction with acrylic acid Bisphenol F epoxy (meth) acrylate obtained by epoxy ring-opening reaction with (meth) acrylic acid, tetrabromobisphenol F epoxy (meta) obtained by epoxy ring-opening reaction between tetrabromobisphenol F diglycidyl ether and (meth) acrylic acid ) Acrylate and the like.
Examples of commercially available unsaturated monomers having such a structure include, for example, Biscote # 700, # 540 (above, manufactured by Osaka Organic Chemical Industry Co., Ltd.), Aronix M-208, M-210 (above, Toagosei ( NK ester BPE-100, BPE-200, BPE-500, A-BPE-4 (above, manufactured by Shin-Nakamura Chemical Co., Ltd.), light ester BP-4EA, BP-4PA, epoxy ester 3002M, 3002A, 3000M, 3000A (above, manufactured by Kyoeisha Chemical Co., Ltd.), KAYARAD R-551, R-712 (above, manufactured by Nippon Kayaku Co., Ltd.), BPE-4, BPE-10, BR-42M (above, Daiichi Kogyo Seiyaku Co., Ltd.), Lipoxy VR-77, VR-60, VR-90, SP-1506, SP-1506, SP-1507, SP-1509 SP-1563 (manufactured by Showa Polymer Co., Ltd.), Neopole V779, Neopole V779MA (manufactured by Nippon Iupika Co., Ltd.), and the like.

Examples of the trifunctional or higher functional (meth) acrylate unsaturated monomer include trimethylolpropane litho (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane trioxyethyl (meth) acrylate, and tris (2-acryloyloxy). (Meth) acrylates of trihydric or higher polyhydric alcohols such as ethyl) isocyanurate.
Examples of commercially available trifunctional or higher functional (meth) acrylate unsaturated monomers include, for example, Aronix M305, M309, M310, M315, M320, M350, M360, M408 (above, manufactured by Toagosei Co., Ltd., Biscote # 295, # 300, # 360, GPT, 3PA, # 400 (above, manufactured by Osaka Organic Chemical Industry Co., Ltd.), NK ester TMPT, A-TMPT, A-TMM-3, A-TMM-3L, A-TMMT (above, Shin Nakamura Chemical Co., Ltd.), Light Acrylate TMP-A, TMP-6EO-3A, PE-3A, PE-4A, DPE-6A (above, Kyoeisha Chemical Co., Ltd., KAYARAD PET-30, GPO-303) , TMPTA, TPA-320, DPHA, D-310, DPCA-20, DPCA-60 (above, manufactured by Nippon Kayaku Co., Ltd.) ) And the like.

  From the viewpoint of keeping the viscosity moderate for the (meth) acryloyl group-containing compound. A urethane (meth) acrylate oligomer may be further blended. Examples of the urethane (meth) acrylate include polyether polyols such as polyethylene glycol and polytetramethyl glycol; succinic acid, adipic acid, azelaic acid, sebacic acid, phthalic acid, tetrahydro (anhydrous) phthalic acid, hexahydro (anhydrous) A dibasic acid such as phthalic acid and a diol such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol Polyester polyol obtained by reaction; polyε-caprolactone-modified polyol; polymethylvalerolactone-modified polyol; ethylene glycol, propylene glycol, 1,4-butanedio Alkyl polyols such as ethylene, 1,6-hexanediol and neopentyl glycol; bisphenol A skeleton alkylene oxide modified polyols such as ethylene oxide-added bisphenol A and propylene oxide-added bisphenol A; bisphenols such as ethylene oxide-added bisphenol F and propylene oxide-added bisphenol F F-skeleton alkylene oxide-modified polyol or a mixture thereof and organic polyisocyanates such as tolylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meta ) From hydroxy group-containing (meth) acrylates such as acrylate The urethane (meth) acrylate oligomer etc. which are manufactured are mentioned.

  Examples of commercially available monomers of urethane (meth) acrylate include, for example, Aronix M120, M-150, M-156, M-215, M-220, M-225, M-240, M-245, and M-270. (Above, manufactured by Toagosei Co., Ltd.), AIB, TBA, LA, LTA, STA, Viscoat # 155, IBXA, Viscoat # 158, # 190, # 150, # 320, HEA, HPA, Viscoat # 2000, # 2100 , DMA, Biscote # 195, # 230, # 260, # 215, # 335HP, # 310HP, # 310HG, # 312 (above, manufactured by Osaka Organic Chemical Industry Co., Ltd.), Light Acrylate IAA, LA, S- A, BO-A, EC-A, MTG-A, DMP-A, THF-A, IB-XA, HOA, HOP-A, HOA-MP , HOA-MPE, light acrylate 3EG-A, 4EG-A, 9EG-A, NP-A, 1,6HX-A, DCP-A (manufactured by Kyoeisha Chemical Co., Ltd.), KAYARADTC-110S, HDDA, NPGDA , TPGDA, PEG400DA, MANDA, HX-220, HX-620 (manufactured by Nippon Kayaku Co., Ltd.), FA-511A, 512A, 513A (manufactured by Hitachi Chemical Co., Ltd.), VP (manufactured by BASF), ACMO, DMAA, DMAPAA (manufactured by Kojin Co., Ltd.) and the like.

  The urethane (meth) acrylate oligomer is obtained as a reaction product of (a) hydroxy group-containing (meth) acrylate, (b) organic polyisocyanate, and (c) polyol, but (a) hydroxy group-containing ( A reaction product obtained by reacting (meth) acrylate with (b) organic polyisocyanate and then (c) polyol is preferable.

  Examples of the photo radical polymerization initiator include acetophenone, acetophenone benzyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine. , Carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4′-dimethoxybenzophenone, 4,4′-diaminobenzophenone, Michler's ketone, benzoin propyl ether, benzoin ethyl ether, benzyldimethyl ketal, 1- (4-isopropylphenyl) ) -2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanthone, die Ruthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide Bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, ethyl-2,4,6-trimethylbenzoylethoxyphenylphosphine oxide, and the like.

  Commercially available products of the photo radical polymerization initiator include, for example, Irgacure 184, 369, 651, 500, 819, 907, 784, 2959, CGI 1700, CGI 1750, CGI 11850, CG 24-61, Darocur 116, 1173 (above, Ciba Specialty Chemicals), Lucirin LR8728, 8893X (above BASF), Ubekrill P36 (UCB), KIP150 (Lamberti) and the like. Among these, Lucirin LR8883X is preferable from the viewpoint of being liquid and easily dissolved and having high sensitivity.

  0.01-10 mass% is preferable in the whole composition which comprises resin, and, as for the compounding quantity of the said radical photopolymerization initiator, 0.5-7 mass% is more preferable. When the blending amount exceeds 10% by mass, the curing characteristics of the composition, the mechanical and optical characteristics of the cured product, and the handleability may be deteriorated. When the blending amount is less than 0.01% by mass, the curing rate is decreased. May decrease.

A photosensitizer can be further blended in the composition constituting the resin. Examples of the photosensitizer include triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, and 4-dimethylaminobenzoate. An isoamyl acid etc. are mentioned.
As a commercial item of the said photosensitizer, Ubekrill P102, 103, 104, 105 (above, the product made from UCB) etc. are mentioned, for example.

  In addition to the above components, various additives include, for example, antioxidants, ultraviolet absorbers, light stabilizers, silane coupling agents, coating surface improvers, thermal polymerization inhibitors, leveling agents, surfactants, and coloring agents. An agent, a storage stabilizer, a plasticizer, a lubricant, a solvent, a filler, an anti-aging agent, a wettability improver, a release agent, and the like can be blended as necessary.

Examples of the antioxidant include Irganox 1010, 1035, 1076, 1222 (above, manufactured by Ciba Specialty Chemicals Co., Ltd.), Antigen P, 3C, FR, GA-80 (manufactured by Sumitomo Chemical Co., Ltd.), and the like. Is mentioned.
Examples of the ultraviolet absorber include Tinuvin P, 234, 320, 326, 327, 328, 329, 213 (above, manufactured by Ciba Specialty Chemicals Co., Ltd.), Seesorb 102, 103, 110, 501, 202, 712. 704 (above, manufactured by Sipro Kasei Co., Ltd.).
Examples of the light stabilizer include Tinuvin 292, 144, 622LD (manufactured by Ciba Specialty Chemicals Co., Ltd.), Sanol LS770 (manufactured by Sankyo Co., Ltd.), Sumisorb TM-061 (Sumitomo Chemical Co., Ltd.). Manufactured) and the like.
Examples of the silane coupling agent include γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and commercially available products such as SH6062, 6030 (above, Toray Dow Corning). -Silicone Co., Ltd.), KBE903, 603, 403 (above, Shin-Etsu Chemical Co., Ltd.).
Examples of the coating surface improver include silicone additives such as dimethylsiloxane polyether and nonionic fluorosurfactants.
Commercially available products of the silicone additive include DC-57, DC-190 (above, manufactured by Dow Corning), SH-28PA, SH-29PA, SH-30PA, SH-190 (above, Toray Dow Corning Silicone ( Co., Ltd.), KF351, KF352, KF353, KF354 (above, manufactured by Shin-Etsu Chemical Co., Ltd.), L-700, L-7002, L-7500, FK-024-90 (above, made by Nihon Unicar Co., Ltd.) ), Commercial products of nonionic fluorosurfactants include FC-430, FC-171 (above 3M Co., Ltd.), MegaFuck F-176, F-177, R-08 (above, Dainippon Ink) Etc.).
Examples of the release agent include Prisurf A208F (Daiichi Kogyo Seiyaku Co., Ltd.).

The organic solvent used for adjusting the resin liquid viscosity of the resin is not particularly limited as long as it can be mixed without unevenness such as precipitates, phase separation, and cloudiness when mixed with the resin liquid, Examples thereof include acetone, methyl ethyl ketone, methyl isobutyl ketone, ethanol, propanol, butanol, 2-methoxyethanol, cyclohexanol, cyclohexane, cyclohexanone, toluene and the like. These may be used individually by 1 type as needed, and 2 or more types may be mixed and used for them.
When the organic solvent is added, it is necessary to dry and evaporate the organic solvent during the manufacturing process of the product. However, if a large amount of residual solvent remains in the product, the mechanical properties of the product deteriorate. There is also a concern that the organic solvent evaporates and diffuses during use as a product, causing bad odor and adverse health effects. For this reason, as the organic solvent, those having a high boiling point are not preferable because the residual solvent amount increases. On the other hand, if the boiling point is too low, it will evaporate violently, resulting in rough surface conditions, condensation water adhering to the surface of the composition due to the heat of vaporization during drying, resulting in surface defects, and vapor concentration It becomes higher and the risk of ignition etc. increases.
Therefore, the boiling point of the organic solvent is preferably 50 to 150 ° C, more preferably 70 to 120 ° C. Specifically, as the organic solvent, methyl ethyl ketone (bp. 79.6 ° C.), 1-propanol (bp. 97.2 ° C.) and the like are preferable from the viewpoint of the solubility of the raw material and the boiling point.

  The amount of the organic solvent added to the resin liquid depends on the type of the solvent and the viscosity of the resin liquid before the addition of the solvent, but usually 10 to 40% by mass in order to sufficiently improve the coatability. And 15-30 mass% is preferable. When the addition amount is less than 10% by mass, the effect of reducing the viscosity and the effect of increasing the coating amount are so small that the coatability may not be sufficiently improved. On the other hand, when the added amount exceeds 40 masses, the viscosity is too low and the liquid may flow on the sheet to cause unevenness, or the liquid may rotate around the back surface of the sheet. In addition, the product cannot be sufficiently dried in the drying process, and a large amount of organic solvent remains in the product, resulting in deterioration of product function, volatilization during product use, generating odors, and adverse health effects. Concerns arise.

The resin liquid can be produced by mixing the respective components by a conventional method, and can be produced by heating and dissolving as required.
The viscosity of the resin liquid thus prepared is usually 10 to 50,000 mPa · s / 25 ° C., but when the resin liquid is supplied to a substrate or an embossing roll, if the viscosity is too high, It becomes difficult to supply the composition uniformly, and when manufacturing lenses, uneven coating, undulation, and air bubbles are mixed in, making it difficult to obtain the desired lens thickness, and sufficient lens performance It cannot be demonstrated. In particular, this tendency becomes remarkable when the line speed is increased. Therefore, in this case, the liquid viscosity is preferably low, preferably 10 to 100 mPa · s, and more preferably 10 to 50 mPa · s. Such a low viscosity can be adjusted by adding an appropriate amount of the organic solvent. Further, the viscosity can be adjusted by setting the temperature of the coating solution to be kept warm.
On the other hand, if the viscosity after evaporation of the solvent is too low, it may be difficult to control the lens thickness when embossing the die, and a uniform lens with a certain thickness may not be formed. Accordingly, in this case, the liquid viscosity is preferably high, and is preferably 100 to 3,000 mPa · s.
When the organic solvent is mixed, by providing a step of evaporating the organic solvent by heating and drying between the steps of supplying the resin solution and embossing the embossing roll, when supplying the resin solution, The liquid can be supplied uniformly with a low viscosity, and when embossing with an embossing roll, it is possible to uniformly emboss with a resin liquid obtained by drying an organic solvent and increasing the viscosity.

  The cured product obtained by curing the resin liquid with radiation has a refractive index at 25 ° C. of preferably 1.55 or more, and more preferably 1.56 or more. If the refractive index is less than 1.55, sufficient front luminance may not be ensured when an optical functional sheet is formed.

<Other members>
The backlight unit may include other members as necessary. Examples of other members include a reflector, a diffuser, and a diffuser sheet (FIGS. 11 and 12).
Here, you may form a prism body on the surface of diffusion function members, such as a diffusion plate and a diffusion sheet. As a result, the optical functional sheet and the diffusion functional member can be integrated, and thus the manufacturing cost can be reduced. In addition, the prism body may be formed on any surface of the diffusion functional member on the surface on the side of the linear light source and on the surface opposite to the linear light source.

<Relationship between linear light source and optical functional sheet>
FIG. 3A is a diagram illustrating an arrangement relationship between the optical functional sheet of FIG. 1 and a linear light source.
In the arrangement relationship between the optical functional sheet 1 and the linear light source 30 as shown in FIG. 3A, f (p) includes one linear light source (for example, the linear light source 30A) among a plurality of linear light sources. An optical function of an intersection line 40 (a linear light source (for example, linear light source 30A) of a plurality of linear light sources) between a plane orthogonal to the optical functional sheet 1 and a plane including the optical functional sheet 1 Projection line 40 on the active sheet 1) and the most intersecting line 40 excluding the virtual image on the intersecting line 40 among the virtual images in the optical functional sheet 1 expressed from one linear light source (for example, the linear light source 30A). The distance from the near virtual image (for example, virtual image 32A) is shown. This f (p) is the refractive index n ′ of the optical functional sheet 1, the slope angle (cross-sectional angle) θ of the exit surface 31 of the prism body 4, the linear light source 30 and the optical function, as in the following formula (1). The distance d from the center of the linear light source 30 to the prism 4 (fine shape) base of the optical functional sheet 1 and the distance D between the optical functional sheet 1 and the observation point. It is determined. However, an error of ± 1 mm or more occurs in f (p) except for the conditions of d = 0 to 30 mm, n ′ = 1.5 to 1.7, θ = 40 ° to 50 °, and D = 250 mm or less.

f (p) ≈0.557d + 27.9 n ′ + 0.473θ−65.7 (1)
Here, the virtual image 32 in the optical functional sheet 1 developed from the linear light source 30 is a linear light source when the linear light source 30 is viewed from the observation point through the optical functional sheet 1 as shown in FIG. It is an image that appears at a position different from the actual position of 30.

Therefore, the optimal virtual image distribution according to the pitch p of the linear light source 30 (when the brightness (luminance) of the virtual image 32 in the optical functional sheet 1 developed from the linear light source 30 is substantially equal, the distance between adjacent virtual images Can be selected to increase the diffusibility. Here, the slope angle (cross-section angle) θ is the angle of the shape cross section of the prism body 4, and thus the diffusivity is adjusted without affecting the light collection performance by rotating the optical functional sheet 1. You can also.
Moreover, when the brightness (luminance) of the virtual image 32 in the optical functional sheet 1 developed from the plurality of linear light sources 30 is not constant, the distance from the adjacent virtual image 32 is appropriately changed depending on the brightness (luminance) of the virtual image 32. It is desirable. Specifically, as shown in FIG. 3B, the optical functional sheet expressed from a plurality of linear light sources 30 with the maximum luminance at the center of the backlight unit in the optical functional sheet 1 being B _max and the minimum luminance being B _min. A second virtual image adjacent to the first virtual image, where A ₁ is the peak position of the first virtual image and the peak height is H ₁ (peak luminance B ₁ −minimum luminance B _min ) among the plurality of virtual images 32 in FIG. , A ₂ , the peak height is H ₂ (peak luminance B ₂ −minimum luminance B _min ), the peak position of the third virtual image adjacent to the second virtual image is A ₃ , and the peak height is H _3. (Peak luminance B ₃ -minimum luminance B _min ), the peak position of the fourth virtual image adjacent to the third virtual image is A ₄ , and the peak height is H ₄ (peak luminance B ₄ -minimum luminance B _min ), Adjacent to the fourth virtual image _{A 5} The peak position of the virtual image of the peak height _{H 5} (peak brightness _{B 5} - minimum luminance _{B min)} If _{a, (H 1 + H 2)} / (A 2 -A 1), (H 2 + H 3 ) / (A ₃ −A ₂ ), (H ₃ + H ₄ ) / (A ₄ −A ₃ ), and (H ₄ + H ₅ ) / (A ₅ −A ₄ ) A distance d between the linear light source 30 and the optical functional sheet 1 is selected.
However, the virtual image 32 refers to a peak whose peak height H _n satisfies the condition of H _n ≧ 0.3 × (B _max −B _min ), and the luminance distribution diagram of FIG. The luminance distribution in the optical functional sheet when a plate is not provided is shown.
The results calculated based on the values shown in FIG. 3B are shown below.
(H ₁ + H ₂ ) / (A ₂ −A ₁ ) = (300 + 300) / 6 = 100
(H ₂ + H ₃ ) / (A ₃ −A ₂ ) = (300 + 100) / 4 = 100
(H ₃ + H ₄ ) / (A ₄ −A ₃ ) = (100 + 100) / 2 = 100
(H ₄ + H ₅ ) / (A ₅ −A ₄ ) = (100 + 300) / 4 = 100
Here, (H ₁ + H ₂ ) / (A ₂ −A ₁ ), (H ₂ + H ₃ ) / (A ₃ −A ₂ ), (H ₃ + H ₄ ) / (A ₄ −A ₃ ), and ( The value (= 100) of H ₄ + H ₅ ) / (A ₅ −A ₄ ) is preferably as small as possible.
In addition, since the position and brightness of the peak are unclear due to the influence of shading at the backlight unit end, the peak height of the adjacent virtual images (the (n-1) th virtual image and the (nth) virtual image) in the center of the backlight unit. The ratio of the sum of (H _n-1 + H _n ) and the peak position interval (A _n -A _n-1 ) of adjacent virtual images is made substantially equal.
Incidentally, in FIG. 3B, since the minimum value of the luminance waveform are all constant value (minimum brightness _{B min),} the peak height _{H n} - but is calculated as (peak brightness _{B n} lowest luminance _{B min),} As shown in FIG. 3C, when the minimum values of the luminance waveforms are different, the peak height H is calculated as (peak luminance B _n -luminance B _T ). However, the brightness of the intersection T between the straight line R ′ (the straight line connecting the minimum value P serving as the peak start point and the minimum value Q serving as the peak end point) and the straight line S (perpendicular line passing through the peak position) is defined as B _T. .
Hereinafter, the backlight central portion will be described.
As shown in FIG. 3D, the number of the plurality of linear light sources is N (even), the leftmost linear light source is the first linear light source, and the linear light source adjacent to the first linear light source is the first. Two linear light sources, a linear light source adjacent to the ( N- 2) th linear light source, a linear light source adjacent to the ( N- 1) th linear light source, and a linear light source adjacent to the ( N- 1) th linear light source When the N-th linear light source is used, three linear light sources of ( N / 2-1) linear light source, ( N / 2) linear light source, and ( N / 2 + 1) linear light source are used. The area to be included is the center of the backlight. For example, as shown in FIG. 3E, when there are eight linear light sources, the third linear light source, the fourth linear light source, and the fifth linear light source are used as the backlight central portion.
Also, as shown in FIG. 3F, the number of the plurality of linear light sources is N (odd number), and the leftmost linear light source is the first linear light source, and the linear light source adjacent to the first linear light source. the second linear light source, ... the (N -2) linear light source first linear light source adjacent to the (N -1) linear light source, the (N -1) linear adjacent the linear light source When the light source is the Nth linear light source, the (( N + 1) / 2-1) linear light source, the (( N + 1) / 2) linear light source, and the (( N + 1) / 2 + 1) A region including the three linear light sources of the linear light source is defined as a backlight central portion. For example, as shown in FIG. 3G, when there are seven linear light sources, the third linear light source, the fourth linear light source, and the fifth linear light source are set as the backlight central portion.

  The same number of virtual images as the number of exit surfaces of the prism body 4 appear (except when the virtual images overlap). Therefore, in the case of a single layer, in order to improve the diffusion performance, the prism body 4 having a quadrangular pyramid shape is preferable to the prism body 4 in which the V groove is formed.

For example, as shown in FIG. 4, the prism body 4 has two first emission surfaces 4 b and 4 c that face each other and two second emission surfaces 4 a and 4 d that face each other. 1 of emitting surface 4b, 4c of the area _{S 4b,} the sum _S 4b _{+ S 4c} of _{S 4c} is a second exit surface 4a, 1 single area _S 4a of _4d, equal to _{S 4d,} concave or convex bottom aspect ratio AR Is a substantially quadrangular pyramid of 1.5, the prism bodies 4 are arranged so that the arrangement direction of the prism bodies 4 and the orientation direction of the linear light source 30 are parallel (inclination angle 0 °). It is preferable to develop three virtual images from two linear light sources (for example, the linear light source 30A) and further optimize the distance d between the optical functional sheet 1 and the linear light source 30. Thereby, higher diffusibility can be obtained. Under this condition, d, n ′ and θ in the equation (1) are set so that f (p) = p / 3 (FIG. 5) or f (p) = 2 × p / 3 (FIG. 6). By determining, the luminance unevenness of the linear light source 30 can be reduced most. The bottom aspect ratio AR is not limited to 1.5, and may be in the range of 1 <AR ≦ 5. However, in AR1.5, three virtual images having the same brightness are generated for one linear light source. Therefore, unevenness can be reduced by making the interval between the virtual images substantially equal. Therefore, it is not always optimal to set the virtual images at substantially equal intervals.

For example, when the prism body 4 is a concave or convex regular quadrangular pyramid having a bottom aspect ratio AR of 1.0 as shown in FIG. Arranged so that the angle is 18.4 ° (= tan ⁻¹ (1/3)) (FIG. 8), four virtual images are expressed from one linear light source (for example, linear light source 30A), Furthermore, it is preferable to optimize the distance d between the optical functional sheet 1 and the linear light source 30. Under this condition, luminance unevenness of the linear light source 30 is most reduced by determining d, n ′ and θ in the equation (1) so that f (p) = p / (8 × sin 18.4 °). can do. The bottom aspect ratio AR is not limited to 1.0, and may be in the range of 1 ≦ AR ≦ 5. However, if AR is 1.0, four virtual images having the same brightness are generated with respect to one linear light source. Therefore, unevenness can be reduced by setting the intervals between the virtual images to be approximately equal, but AR is 1.0. In other cases, since the brightness (brightness) of the virtual image becomes non-uniform, it is not always optimal to set the virtual images at substantially equal intervals.

For example, when the prism sheet BEFII (manufactured by Sumitomo 3M Limited) (FIG. 9) having a concave or convex V-groove is used as the optical functional sheet 1, the arrangement direction of the prism bodies 4 (V-groove) (The forming direction) and the linear light source 30 are arranged in parallel (inclination angle 0 °), two virtual images are developed from one linear light source (for example, the linear light source 30A), and the optical function It is preferable to optimize the distance d between the conductive sheet 1 and the linear light source 30. Under this condition, the linear light source 30 is determined by determining d, n ′ and θ in the equation (1) so that f (p) = p / 4 or f (p) = 3 × p / 4. Brightness unevenness can be reduced most.

Further, for example, two prism sheets BEFII (manufactured by Sumitomo 3M Limited) having concave or convex V-grooves are used as the optical functional sheet 1 and arranged so that the ridge lines of the two prism bodies 4 are orthogonal to each other. The inclination angle between the arrangement direction of the prism bodies 4 of one of the prism sheets BEFII (for example, the prism sheet BEFII on the linear light source 30 side) and the linear light source 30 is 26.6 ° (= tan ⁻¹ (1/2 )), Four virtual images are developed from one linear light source (for example, linear light source 30A), and the distance d between the optical functional sheet 1 and the linear light source 30 is optimized. Also good. Thereby, higher condensing property and diffusibility can be obtained, and front luminance can be improved. Under this condition, f (p) = p / (8 × (sin 26.6 ° + cos 26.6 °)) or f (p) = p / (6.5 × (sin 26.6 ° + cos 26.6 °) ), The luminance unevenness of the linear light source 30 can be most reduced by determining d, n ′ and θ in the equation (1).

Further, in order to improve productivity and diffusibility, the apex portion of the prism body 4 may be flat or spherical, or the slope angle of the prism body 4 (angle formed by the exit surface with respect to the reference surface 3b) θ may be reduced. . However, in consideration of the light collecting property, the slope angle θ is 40 to 50 °, preferably 44 to 46 °. When it is necessary to improve productivity and diffusibility even when the light condensing property is lowered, the slope angle θ is preferably 45 ° or less in order to suppress side lobes.
In addition, when the number of the output surfaces in the prism body 4 is an odd number, the angle (vertical angle) formed with the opposed output surfaces is not 90 °, and the light condensing performance is lowered, which is not preferable.
Further, when the prism body 4 is a regular hexagonal pyramid, it is not possible to generate virtual images at equal intervals, but it is possible to generate six virtual images, so the same unevenness elimination effect can be expected.
Further, when the prism body 4 is a regular heptagon or more, the prism bodies cannot be arranged without a gap, and thus it is difficult to manufacture.
When the light source is not a linear light source but a point light source, the virtual line direction connecting the point light sources is set as the alignment direction of the linear light source.
Moreover, the light condensing function and the light diffusing function can be improved by mixing diffusing particles in the whole or a part of the optical functional sheet 1.
Further, as the optical functional sheet 1 is moved from the center to the end, the slope angle θ is slightly decreased (for example, the center is about 47 ° and the end is about 43 °), thereby further improving the diffusibility. The diffusibility can also be improved by slightly increasing the pitch of the linear light sources 30 as the distance from the center of the optical functional sheet 1 increases.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
After a 200 μm thick sheet made of polycarbonate resin (Mitsubishi Chemical Corporation, refractive index 1.59) is formed by extrusion molding, the length ratio is 1.5 (bottom width 50 μm) at 200 ° C. × 2 MPa × 10 min. An optical functional sheet (FIG. 4) having a concave substantially quadrangular pyramid transferred thereon was obtained by hot pressing with a mold having a convex substantially quadrangular pyramid of × 75 μm and a height of 25 μm (inclination angle θ of 45). °). Optical functionality is obtained by combining the obtained optical functional sheet, a cold cathode tube as a plurality of linear light sources arranged in parallel, and a reflector (light box) that reflects light from the cold cathode tube. A backlight unit in which the optical functional sheet was arranged so that the angle between the arrangement direction of the prism bodies (regular quadrangular pyramids) on the sheet and the orientation direction of the cold cathode tubes was parallel (0 °) was produced. Here, the distance d between the cold cathode tube and the optical functional sheet is 13.5 mm, the distance D between the optical functional sheet and the observation point (color luminance meter described later) is 350 mm, and the arrangement pitch p of the cold cathode tubes The cold-cathode tube was turned on in a state of 23 mm, and the luminance in the optical functional sheet was measured at an equal interval in the vertical direction with the cold-cathode tube using a color luminance meter (Topcon Co., Ltd., BM-7FAST). In addition to obtaining an average luminance value and a standard deviation of luminance between one pitch of linear light sources from directly above the linear light source to immediately above the adjacent linear light source, luminance unevenness was evaluated according to the following evaluation criteria.
Brightness unevenness value: Brightness standard deviation / Luminance average value <Brightness unevenness evaluation criteria>
◎: No luminance unevenness ○: Some luminance unevenness Δ: Brightness unevenness ×: Large luminance unevenness As a result, the average luminance value is 9,240 cd, the luminance standard deviation is 3,220 cd, and the luminance standard deviation / luminance average The value was 0.348, and the luminance unevenness evaluation was ◯ (Table 1).
In an actual display, the diffusion degree is further increased by a diffusion plate, a diffusion sheet, etc. In this embodiment, in order to emphasize the luminance unevenness and easily confirm the effect of reducing the luminance unevenness, Sheets are not used.

(Example 2)
A backlight unit was produced in the same manner as in Example 1 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 28.5 mm, and the luminance was measured. As a result, the luminance average value was 9,310 cd, the luminance standard deviation was 3,240 cd, the luminance standard deviation / luminance average value was 0.348, and the luminance unevenness evaluation was ◯ (Table 1).

(Comparative Example 1)
A backlight unit was produced in the same manner as in Example 1 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 5.0 mm, and the luminance was measured. As a result, the luminance average value was 9,180 cd, the luminance standard deviation was 5,020 cd, the luminance standard deviation / luminance average value was 0.547, and the luminance unevenness evaluation was x (Table 1).

(Example 3)
A backlight unit was produced in the same manner as in Example 1 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 11.0 mm, and the luminance was measured. As a result, the luminance average value was 9,370 cd, the luminance standard deviation was 3,530 cd, the luminance standard deviation / luminance average value was 0.377, and the luminance unevenness evaluation was Δ (Table 1).

Example 4
A backlight unit was produced in the same manner as in Example 1 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was set to 16.0 mm, and the luminance was measured. As a result, the luminance average value was 9,100 cd, the luminance standard deviation was 3,470 cd, the luminance standard deviation / luminance average value was 0.381, and the luminance unevenness evaluation was ◯ (Table 1).

(Comparative Example 2)
A backlight unit was produced in the same manner as in Example 1 except that the distance d between the cold cathode tube and the optical functional sheet was 21.0 mm, and the luminance was measured. As a result, the luminance average value was 9,150 cd, the luminance standard deviation was 5,560 cd, the luminance standard deviation / luminance average value was 0.608, and the luminance unevenness evaluation was x (Table 1).

(Example 5)
A backlight unit was produced in the same manner as in Example 1 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 26.0 mm, and the luminance was measured. As a result, the luminance average value was 9,220 cd, the luminance standard deviation was 3,470 cd, the luminance standard deviation / luminance average value was 0.376, and the luminance unevenness evaluation was ◯ (Table 1).

(Example 6)
A backlight unit was produced in the same manner as in Example 1 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 31.0 mm, and the luminance was measured. As a result, the luminance average value was 9,160 cd, the luminance standard deviation was 3,530 cd, the luminance standard deviation / luminance average value was 0.385, and the luminance unevenness evaluation was Δ (Table 1).

(Comparative Example 3)
A backlight unit was produced in the same manner as in Example 1 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 45.0 mm, and the luminance was measured. As a result, the luminance average value was 9,150 cd, the luminance standard deviation was 8,380 cd, the luminance standard deviation / luminance average value was 0.916, and the luminance unevenness evaluation was x (Table 1).

  It should be noted that the expression (1) is set so that f (p) = p / 3 or f (p) = 2 × p / 3 under the conditions of Examples 1 to 6 and Comparative Examples 1 to 3 described above. When the optimal value of d is calculated using the above, d is 13.9 mm or 27.6 mm, and in the range of 8.9 to 18.9 mm and 22.6 to 32.6 mm, a good luminance standard deviation / luminance average value ( 0.540 or less) was obtained, and the luminance unevenness evaluation was also ◯ or Δ.

(Example 7)
Instead of the optical functional sheet (FIG. 4) to which the concave substantially quadrangular pyramid is transferred, a prism sheet BEFII (manufactured by Sumitomo 3M Limited) (FIG. 9) is used. A backlight unit was produced in the same manner as in Example 1 except that the distance d to the sheet was 9.8 mm, and the luminance was measured. As a result, the luminance average value was 10,130 cd, the luminance standard deviation was 4,920 cd, the luminance standard deviation / luminance average value was 0.486, and the luminance unevenness evaluation was Δ (Table 1).

(Example 8)
A backlight unit was produced in the same manner as in Example 7 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 32.0 mm, and the luminance was measured. As a result, the luminance average value was 10,430 cd, the luminance standard deviation was 4,825 cd, the luminance standard deviation / luminance average value was 0.463, and the luminance unevenness evaluation was Δ (Table 1).

Example 9
A backlight unit was produced in the same manner as in Example 7 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 5.0 mm, and the luminance was measured. As a result, the luminance average value was 10,090 cd, the luminance standard deviation was 5,438 cd, the luminance standard deviation / luminance average value was 0.539, and the luminance unevenness evaluation was Δ (Table 1).

(Example 10)
A backlight unit was produced in the same manner as in Example 7 except that the distance d between the cold cathode tube and the optical functional sheet was 8.0 mm, and the luminance was measured. As a result, the luminance average value was 10,320 cd, the luminance standard deviation was 5,016 cd, the luminance standard deviation / luminance average value was 0.486, and the luminance unevenness evaluation was Δ (Table 1).

(Example 11)
A backlight unit was produced in the same manner as in Example 7 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 12.0 mm, and the luminance was measured. As a result, the luminance average value was 10,500 cd, the luminance standard deviation was 4,959 cd, the luminance standard deviation / luminance average value was 0.472, and the luminance unevenness evaluation was Δ (Table 1).

(Comparative Example 4)
A backlight unit was produced in the same manner as in Example 7 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 21.0 mm, and the luminance was measured. As a result, the luminance average value was 10,250 cd, the luminance standard deviation was 8,744 cd, the luminance standard deviation / luminance average value was 0.853, and the luminance unevenness evaluation was x (Table 1).

(Example 12)
A backlight unit was produced in the same manner as in Example 7 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 30.0 mm, and the luminance was measured. As a result, the luminance average value was 10,210 cd, the luminance standard deviation was 4,911 cd, the luminance standard deviation / luminance average value was 0.481, and the luminance unevenness evaluation was Δ (Table 1).

(Example 13)
A backlight unit was produced in the same manner as in Example 7 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 34.0 mm, and the luminance was measured. As a result, the luminance average value was 10,370 cd, the luminance standard deviation was 4,889 cd, the luminance standard deviation / luminance average value was 0.471, and the luminance unevenness evaluation was Δ (Table 1).

(Comparative Example 5)
A backlight unit was produced in the same manner as in Example 7 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 45.0 mm, and the luminance was measured. As a result, the luminance average value was 10,210 cd, the luminance standard deviation was 8,382 cd, the luminance standard deviation / luminance average value was 0.821, and the luminance unevenness evaluation was x (Table 1).

  Using the formula (1), f (p) = p / 4 or f (p) = 3 × p / 4 under the conditions of Examples 7 to 13 and Comparative Examples 4 and 5 described above. When the optimum value of d is calculated, d is 10.4 mm or 31.1 mm. In the range of 5.4 to 15.4 mm and 26.1 to 36.1 mm, a good luminance standard deviation / luminance average value (0. 540 or less) was obtained, and the luminance unevenness evaluation was also ◯ or Δ.

(Example 14)
In place of the optical functional sheet (FIG. 4) to which the concave substantially square pyramid is transferred, an optical functional sheet to which the concave regular square pyramid is transferred is used, and the arrangement direction of the prism bodies (substantially square pyramids) in this optical functional sheet The optical functional sheet is arranged so that the angle between the cold cathode tube and the orientation direction of the cold cathode tube is 18.4 ° (FIG. 8), and the distance d between the cold cathode tube and the optical functional sheet is set to 16.3 mm. Manufactured a backlight unit in the same manner as in Example 1, and measured the luminance. As a result, the luminance average value was 9,410 cd, the luminance standard deviation was 2,430 cd, the luminance standard deviation / luminance average value was 0.258, and the luminance unevenness evaluation was ◎ (Table 1).

(Example 15)
A backlight unit was produced in the same manner as in Example 14 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 27.0 mm, and the luminance was measured. As a result, the luminance average value was 9,190 cd, the luminance standard deviation was 2,834 cd, the luminance standard deviation / luminance average value was 0.308, and the luminance unevenness evaluation was ◎ (Table 1).

(Comparative Example 6)
A backlight unit was produced in the same manner as in Example 14 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 5.0 mm, and the luminance was measured. As a result, the luminance average value was 9,180 cd, the luminance standard deviation was 5,456 cd, the luminance standard deviation / luminance average value was 0.594, and the luminance unevenness evaluation was x (Table 1).

(Example 16)
A backlight unit was produced in the same manner as in Example 14 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 14.0 mm, and the luminance was measured. As a result, the luminance average value was 9,050 cd, the luminance standard deviation was 2,766 cd, the luminance standard deviation / luminance average value was 0.306, and the luminance unevenness evaluation was ◯ (Table 1).

(Example 17)
A backlight unit was produced in the same manner as in Example 14 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 18.0 mm, and the luminance was measured. As a result, the luminance average value was 9,260 cd, the luminance standard deviation was 2,590 cd, the luminance standard deviation / luminance average value was 0.280, and the luminance unevenness evaluation was ◎ (Table 1).

(Example 18)
A backlight unit was produced in the same manner as in Example 14 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 22.0 mm, and the luminance was measured. As a result, the luminance average value was 9,560 cd, the luminance standard deviation was 4,000 cd, the luminance standard deviation / luminance average value was 0.418, and the luminance unevenness evaluation was Δ (Table 1).

(Example 19)
A backlight unit was produced in the same manner as in Example 14 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 25.0 mm, and the luminance was measured. As a result, the luminance average value was 9,440 cd, the luminance standard deviation was 2,898 cd, the luminance standard deviation / luminance average value was 0.307, and the luminance unevenness evaluation was ◯ (Table 1).

(Example 20)
A backlight unit was produced in the same manner as in Example 14 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 29.0 mm, and the luminance was measured. As a result, the luminance average value was 9,640 cd, the luminance standard deviation was 2,910 cd, the luminance standard deviation / luminance average value was 0.302, and the luminance unevenness evaluation was ◯ (Table 1).

( Reference Example 21)
A backlight unit was produced in the same manner as in Example 14 except that the distance d between the cold cathode fluorescent lamp and the optical functional sheet was 34.0 mm, and the luminance was measured. As a result, the luminance average value was 9,090 cd, the luminance standard deviation was 4,894 cd, the luminance standard deviation / luminance average value was 0.538, and the luminance unevenness evaluation was Δ (Table 1).

F (p) = p / (8 × sin18.4 °) or f (p) = p / (5 × sin18. Under the conditions of Examples 14 to 20, Reference Example 21, and Comparative Example 6 described above. When the optimum value of d is calculated using Equation (1) to be 4 °), d is 16.4 mm or 26.3 mm, which is 11.4 to 21.4 mm and 21.3 to 31.3 mm. In the range, a good luminance standard deviation / luminance average value (0.540 or less) was obtained, and the luminance unevenness evaluation was also ◎, ○, or Δ.

  The prism body 4 has a substantially quadrangular pyramid shape with a bottom aspect ratio AR of 1.5 (FIG. 4), a V-groove formed shape (FIG. 9), and a regular square pyramid with a bottom aspect ratio AR of 1.0. FIG. 10 shows a relation graph (simulation calculation result of unevenness evaluation) between the distance d between the linear light source and the optical functional sheet and the standard deviation of brightness (luminance unevenness) in the case of the shape (FIG. 8). A range of 500 or less from the optimum value of the standard deviation of brightness (minimum value of standard deviation) as the vertical axis of this relationship graph is considered to be sufficiently effective, and (the optimum of d obtained from (Equation (1)). Value) ± 5 mm) was defined as the allowable range of d. However, in consideration of a general reflector, the number of virtual images increases. Therefore, it is preferable to reduce the lower limit of the allowable range of d by 3 mm ((optimum value of d obtained from Expression (1)) − 8 mm). In consideration of a general diffusion plate or diffusion sheet, it is preferable to increase the upper limit of the allowable range of d by 3 mm ((optimum value of d obtained from Expression (1)) + 8 mm).

The backlight unit of the present invention can improve the light diffusion function and reduce the unevenness of the linear light source without causing deterioration of the light collecting function, generation of side lobes, decrease in productivity, etc. In various displays such as a display device and an organic EL, a display device, a lighting device, and the like, it can be suitably used for adjusting the light emission efficiency and emission characteristics.
In addition, an optical functional sheet can also be made into a reflecting plate by making the apex angle of the optical functional sheet in a backlight into about 170 degrees, and vapor-depositing a metal. Thereby, it is possible to reduce luminance unevenness, improve the utilization efficiency of reflected light, and prevent moire.

FIG. 1 is a perspective view showing a configuration of an optical functional sheet in the backlight unit of the present invention. FIG. 2 is a block diagram illustrating a configuration of a manufacturing apparatus used in the method for manufacturing the optical functional sheet in FIG. FIG. 3A is a diagram illustrating an arrangement relationship between the optical functional sheet of FIG. 1 and a linear light source. 3B, when the brightness (luminance) of the virtual image in the optical functional sheet expressed from the linear light source in FIG. 3A is not constant, the distance from the adjacent virtual image is appropriately changed depending on the brightness (luminance) of the virtual image. FIG. FIG. 3C is a diagram illustrating the peak height. FIG. 3D is a diagram for explaining the central portion of the backlight unit when the number of the plurality of linear light sources is N (even). FIG. 3E is a diagram for explaining the central portion of the backlight unit when the number of the plurality of linear light sources is eight. FIG. 3F is a diagram for explaining a central portion of the backlight unit when the number of the plurality of linear light sources is N (odd number). FIG. 3G is a diagram for explaining the central portion of the backlight unit when the number of the plurality of linear light sources is seven. FIG. 4 is a plan view showing an optical functional sheet in which the shape of the prism body in FIG. 1 is a concave, substantially square pyramid with a length ratio of 1.5. FIG. 5 is a diagram for explaining a virtual image generation position in the optical functional sheet of FIG. 4 when f (p) is p / 3. FIG. 6 is a diagram illustrating a virtual image generation position in the optical functional sheet of FIG. 4 when f (p) is 2p / 3. FIG. 7 is a plan view showing an optical functional sheet in which the prism body in FIG. 1 is a concave regular quadrangular pyramid. FIG. 8 is a plan view showing an optical functional sheet in which the prism body in FIG. 1 is a concave regular quadrangular pyramid, and the prism body arrangement direction is inclined by 18.4 ° with respect to the arrangement direction of the linear light sources. It is. FIG. 9 is a perspective view showing an optical functional sheet in which the prism body in FIG. 1 has a V-groove shape. FIG. 10 is a graph showing a simulation calculation result of unevenness evaluation. FIG. 11 is a diagram illustrating a backlight unit having a reflecting plate. FIG. 12 is a view showing a backlight unit having a diffusion plate and a diffusion sheet. FIG. 13 is a schematic cross-sectional view showing an example of a conventional direct type backlight unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical functional sheet 2 Support body 3 Base material 4 Prism body 30 Linear light source 31 Slope 32 Virtual image 40 Intersection line

Claims (5)

A backlight unit comprising: an optical functional sheet in which a prism structure having a plurality of prism bodies is formed on at least one surface; and a plurality of linear light sources arranged in parallel to the optical functional sheet. ,
In the luminance distribution diagram showing the luminance distribution in the optical functional sheet, the maximum luminance at the central portion of the backlight unit in the optical functional sheet is B _max and the minimum luminance is B _min, and is expressed from the plurality of linear light sources. Among the plurality of virtual images, the peak position of the first virtual image is A ₁ , the peak height is H ₁ , the peak position of the second virtual image adjacent to the first virtual image is A ₂ , and the peak height is H _2. The peak position of the (n−1) th virtual image adjacent to the (n−2) th virtual image is A _n−1 , the peak height is H _n−1, and it is adjacent to the (n−1) th virtual image. If the peak position of the virtual image of the n and _{a n,} the peak height and _{H n,} so that the value is substantially constant _{(H n-1 + H n} ) / (a n -A n-1), the A distance d between the linear light source and the optical functional sheet is selected,
The distance d is
(1) the shape of the prism member is a case of a substantially quadrangular pyramid, Ri parallel der to the orientation direction of the arrangement direction linear light source of the prism body, the virtual image with respect to the linear light source one Is expressed by the following formula (1-1) or the following formula (1-2),
(2) When the shape of the prism bodies is a regular quadrangular pyramid, the arrangement direction of the prism bodies is inclined by an angle X ° with respect to the orientation direction of the linear light sources so as to reduce luminance unevenness, and the linear light sources When four virtual images are expressed for one, it is calculated by the following formula (1-3) or the following formula (1-4),
(3) the shape of the prism body is in the case V groove and the optical functional sheet is one, Ri parallel der to the orientation direction of the arrangement direction linear light source of the prism body, the linear When two virtual images are expressed for one light source, it is calculated by the following formula (1-5) or the following formula (1-6),
(4) In the case where the prism body has a V-groove shape and two optical functional sheets, the angle X at which the arrangement direction of the prism bodies can reduce luminance unevenness with respect to the alignment direction of the linear light source The back is calculated by the following formula (1-7) or the following formula (1-8) when tilted and four virtual images are expressed for one linear light source. Light unit.
However, the peak height H _n refers to the maximum value of the peak, and the virtual image refers to a peak whose peak height H _n satisfies the condition of H _n ≧ 0.3 × (B _max −B _min ), The peak position refers to the position where the peak appears on the horizontal axis indicating the arrangement direction of the plurality of linear light sources in the luminance distribution diagram, and the central part of the backlight unit is the number of the plurality of linear light sources. N (even) lines, the leftmost linear light source being the first linear light source, the linear light source adjacent to the first linear light source being the second linear light source, ... ( N- 2) line When the linear light source adjacent to the linear light source is the ( N- 1) th linear light source and the linear light source adjacent to the ( N- 1) th linear light source is the Nth linear light source, ( N / 2) -1) linear light source, the (N / 2) linear light source, and finger regions including a first (N / 2 + 1) 3 this linear light source of the linear light source The luminance distribution chart, the backlight unit shows the distribution of brightness in an optical functional sheet when not provided with a diffusion sheet and the diffusion plate.
In addition, the formulas (1-1) to (1-8) are expressed by the refractive index “ n ′ ” of the optical functional sheet and the slope angle “θ” of the light exit surface of the light emitted from the linear light source in the prism body. And a line of intersection between a plane that includes one linear light source of the plurality of linear light sources and that is orthogonal to the optical functional sheet and a plane that includes the optical functional sheet, and the one linear It is calculated based on the pitch “p” of the linear light source, which is the distance from the virtual image closest to the intersecting line excluding the intersecting virtual image among the virtual images in the optical functional sheet expressed from the light source.   The ratio between the peak height of one virtual image of a plurality of virtual images expressed from a plurality of linear light sources and the peak height of a virtual image adjacent to the one virtual image and the peak position interval of the adjacent virtual images is approximately The backlight unit according to claim 1 which is equal. In a backlight unit comprising an optical functional sheet in which a prism structure having a plurality of prism bodies is formed on at least one surface, and a plurality of linear light sources arranged in parallel to the optical functional sheet , The linear light source and the optical function so that the brightness of the virtual image in the optical functional sheet expressed from a plurality of linear light sources is substantially equal, and the distance between adjacent virtual images in the optical functional sheet is substantially equal. Distance d with the adhesive sheet is selected,
The distance d is
(1) the shape of the prism member is a case of a substantially quadrangular pyramid, Ri parallel der to the orientation direction of the arrangement direction linear light source of the prism body, the virtual image with respect to the linear light source one Is expressed by the following formula (1-1) or the following formula (1-2),
(2) When the shape of the prism bodies is a regular quadrangular pyramid, the arrangement direction of the prism bodies is inclined by an angle X ° with respect to the orientation direction of the linear light sources so as to reduce luminance unevenness, and the linear light sources When four virtual images are expressed for one, it is calculated by the following formula (1-3) or the following formula (1-4),
(3) the shape of the prism body is in the case V groove and the optical functional sheet is one, Ri parallel der to the orientation direction of the arrangement direction linear light source of the prism body, the linear When two virtual images are expressed for one light source, it is calculated by the following formula (1-5) or the following formula (1-6),
(4) In the case where the prism body has a V-groove shape and two optical functional sheets, the angle X at which the arrangement direction of the prism bodies can reduce luminance unevenness with respect to the alignment direction of the linear light source The back is calculated by the following formula (1-7) or the following formula (1-8) when tilted and four virtual images are expressed for one linear light source. Light unit.
However, the formulas (1-1) to (1-8) are expressed as follows: the refractive index “ n ′ ” of the optical functional sheet, and the slope angle “θ” of the light exit surface of the light emitted from the linear light source in the prism body. And a line of intersection between a plane that includes one linear light source of the plurality of linear light sources and that is orthogonal to the optical functional sheet and a plane that includes the optical functional sheet, and the one linear It is calculated based on the pitch “p” of the linear light source, which is the distance from the virtual image closest to the intersecting line except the virtual image on the intersecting line among the virtual images in the optical functional sheet expressed from the light source. When an area from a plurality of linear light sources to another linear light source adjacent to the linear light source and an area on the emission side toward the optical functional sheet of the area are defined as an area R,
An area from the first linear light source of the plurality of linear light sources to a second linear light source adjacent to the first linear light source, and an emission side of the area toward the optical functional sheet A region R ₁ , a region from the second linear light source to a third linear light source adjacent to the second linear light source, and an exit-side region toward the optical functional sheet in the region And the region R ₂ ,..., The region from the (n−1) -th linear light source to the n-th linear light source adjacent to the n-th linear light source, and the emission toward the optical functional sheet in the region A region on the side, region R _n−1 , a region from the nth linear light source to the (n + 1) th linear light source adjacent to the nth linear light source, and emission toward the optical functional sheet of the region a side region when the region R _n,
The average value of the luminance of the optical functional sheet in the region R _n, the region R value obtained by dividing the standard deviation of the brightness in the optical functional sheet within _n (luminance standard deviation / average luminance value) at 0.540 or less The backlight unit according to claim 3.   The prism body has two first emission surfaces facing each other and two second emission surfaces facing each other, and the sum of the areas of the two first emission surfaces is the second The backlight unit according to any one of claims 1 to 4, wherein the backlight unit is a substantially quadrangular pyramid substantially equal to one area of the emission surface.