JP2008112590A - Backlight unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a backlight unit capable of improving the light diffusing function without lowering the light condensing function, and reducing the irregularity in a linear light source. <P>SOLUTION: This backlight unit includes a plurality of linear light sources, and an optical functionality sheet, on at least one surface of which a prism structure having a plurality of prism members is formed. In a luminance distribution chart showing the distribution of luminance in the optical functionality sheet, a value of (H<SB>n-1</SB>+H<SB>n</SB>)/(A<SB>n</SB>-A<SB>n-1</SB>) is substantially constant. <P>COPYRIGHT: (C)2008,JPO&INPIT

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. 30, 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 direction of 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 without reducing the light collecting function, generating side lobes, reducing productivity, etc., and reducing the linear light source unevenness. For the purpose.

Means for solving the problems are as follows. That is,
<1> A backlight unit comprising a plurality of linear light sources and an optical functional sheet in which a prism structure having a plurality of prism bodies is formed on at least one surface, the luminance distribution in the optical functional sheet The maximum luminance at the center of the backlight unit in the optical functional sheet is Bmax, the minimum luminance is Bmin, and the peak position of the first virtual image expressed from the plurality of linear light sources is A _1. , The peak height is H ₁ , the peak position of the second virtual image 2 adjacent to the first virtual image is A ₂ , the peak height is H ₂ ,... The peak position of the n−1 virtual image is A _n−1 , the peak height is H _n−1 , the peak position of the nth virtual image adjacent to the n−1 virtual image is A _n , and the peak height is H If the _{n, (H n-} + Value of _{H n) / (A n -A} n-1) is a backlight unit, characterized in that a substantially constant.
However, the virtual image refers to a peak whose peak height H _n satisfies the condition of H _n ≧ 0.3 × (Bmax−Bmin), and in the luminance distribution diagram, the backlight unit includes a diffusion sheet and a diffusion plate. The luminance distribution in the optical function sheet when there is no sheet is shown.
In <1>, the value of (H _n−1 + H _n ) / (A _n −A _n−1 ) is substantially constant, so that the light diffusion function is improved without deteriorating the light collecting function, Linear light source unevenness can be reduced.
<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> In a backlight unit including a plurality of linear light sources and an optical functional sheet in which a prism structure having a plurality of prism bodies is formed on at least one surface, the optical expressed from the plurality of linear light sources The backlight unit is characterized in that the brightness of the virtual image in the functional sheet is substantially equal, and the distance between adjacent virtual images in the optical functional sheet is substantially equal.
In <3>, 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. The light diffusion function can be improved and the linear light source unevenness can be reduced without lowering the light intensity.
<4> In the luminance distribution diagram showing the luminance distribution in the optical functional sheet, the second linear light source adjacent to the first linear light source from the first linear light source among the plurality of linear light sources. The region up to the region R ₁ , the region from the second linear light source to the third linear light source adjacent to the second linear light source is the region R ₂ ,. The region from the light source to the nth linear light source adjacent to the nth linear light source is defined as a region Rn _-1 , and the n + 1th linear shape adjacent to the nth linear light source from the nth linear light source. the region up to the light source when the area R _n, in the region of each of the regions R ₁ to R _n, back according to <3> of approximately equal intensity peak heights is present substantially the same number at approximately equal intervals It is a light unit.
<5> In the backlight unit including the diffusion sheet, a region from the first linear light source among the plurality of linear light sources to the second linear light source adjacent to the first linear light source is 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 is a region R ₂ ,..., From the (n−1) th linear light source to the nth line. A region from the n-th linear light source to the n + 1-th linear light source adjacent to the n-th linear light source is a region R _n-1 . is _n, the average value of the luminance of the optical functional sheet in the region R _n, the region and the value obtained by dividing the standard deviation of the brightness in the optical functional sheet in R _n is less than 0.0100 < The backlight unit according to any one of <1> to <4>.
<6> The backlight unit according to any one of <1> to <5>, wherein the arrangement direction of the prism bodies is inclined with respect to the alignment direction of the linear light source.

  According to the present invention, the conventional problems can be solved, and the light diffusion function can be improved and the linear light source unevenness can be reduced without deteriorating the light collecting function, generating side lobes, reducing productivity, etc. It is possible to provide a backlight unit that can 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 when 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 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.
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>
As shown in FIG. 3A, when the shape of the prism body 4 of the optical functional sheet 1 is a concave or convex regular quadrangular pyramid, the brightness of the virtual image in the optical functional sheet 1 expressed from one linear light source is substantially equal. The distance between adjacent virtual images in the optical functional sheet 1 expressed from one linear light source is substantially equal, and thus the luminance of the virtual image in the optical functional sheet 1 expressed from a plurality of linear light sources is substantially equal, The alignment direction of the prism bodies 4 (arrows 33) is the orientation direction of the linear light sources (arrows 34) so that the distances between adjacent virtual images in the optical functional sheet 1 expressed from a plurality of linear light sources are substantially equal. In contrast, the inclination is 18.4 ° (= tan ⁻¹ (1/3)), which is considered to be the most preferable in theory. Thereby, while improving a light-diffusion function, without reducing a condensing function, a linear light source nonuniformity can be reduced. If the arrangement direction of the prism bodies 4 (arrow 33) is not tilted with respect to the alignment direction of the linear light source (arrow 34), the brightness of the virtual image in the middle of the optical functional sheet 1 that appears from one linear light source. The brightness (luminance) is twice the brightness (luminance) of the other two virtual images.
Although FIG. 3A shows the case where the inclination angle between the arrangement direction of the prism bodies 4 (arrow 33) and the alignment direction of the linear light source (arrow 34) is 18.4 °, it is not limited to this. The distance between the linear light source and the optical functional sheet 1 is appropriately adjusted depending on the arrangement and type of the diffusion sheet, the diffusion plate, the reflection plate, and the like.
In addition, when the shape of the prism body 4 of the optical functional sheet 1 is a concave or convex regular quadrangular pyramid, the arrangement direction of the prism bodies 4 (arrow 33) is relative to the alignment direction of the linear light source (arrow 34). An equivalent luminance measurement result can be obtained when tilted by X ° and when tilted by (90-X) °.
When the brightness (luminance) of the virtual image in the optical functional sheet 1 expressed from a plurality of linear light sources is not constant, it is desirable to appropriately change the distance from the adjacent virtual image depending on the brightness (luminance) of the virtual image. Specifically, as shown in FIG. 3B, in the optical functional sheet 1, the maximum luminance at the center of the backlight unit in the optical functional sheet 1 is Bmax and the minimum luminance is Bmin. Of the plurality of virtual images, the peak position of the first virtual image is A ₁ , the peak height is H ₁ (peak luminance B ₁ -minimum luminance Bmin), and the peak position of the second virtual image adjacent to the first virtual image is A ₂ , the peak height is H ₂ (peak luminance B ₂ -minimum luminance Bmin), 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 - a minimum luminance Bmin), a third fourth virtual image a ₄ the peak position of the adjacent virtual _image, a peak height H _{4 (peak} brightness B ₄ - the minimum luminance Bmin), adjacent to the fourth virtual image the peak position of the fifth virtual image a _5, peak Of the _{H 5} (peak brightness _{B 5} - minimum luminance Bmin) case of _{a, (H 1 + H 2)} / (A 2 -A 1), (H 2 + H 3) / (A 3 -A 2), (H The distance from the adjacent virtual image is appropriately changed so that the values of ₃ + H ₄ ) / (A ₄ −A ₃ ) and (H ₄ + H ₅ ) / (A ₅ −A ₄ ) are substantially constant.
However, the virtual image means a peak whose peak height H _n satisfies the condition of H _n ≧ 0.3 × (Bmax−Bmin), and in the luminance distribution diagram of FIG. 3B, the backlight unit includes a diffusion sheet and a diffusion plate. The luminance distribution in the optical function sheet when there is no sheet 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
Where (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”) at the center of the backlight unit unit. The ratio of the sum (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 luminance Bmin), peak height H _n - but is calculated as (peak brightness B _n lowest luminance Bmin), FIG. 3C When the minimum values of the luminance waveforms are different as described above, the peak height H is calculated as (peak luminance B _n -luminance B _T ). However, the brightness of the intersection T of the straight line R (the peak of the starting point and becomes the minimum value P and the peak of the end points and becomes the minimum value Q connecting the straight line) and the straight line S (vertical line passing through the peak position) and 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 (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 the (n / 2-1) linear light source, the (n / 2) linear light source, and the (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.
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. Is 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 light source is the n-th linear light source, the ((n + 1) / 2-1) linear light source, the ((n + 1) / 2) linear light source, and the ((n + 1) / 2 + 1) linear light source A region including the three linear light sources 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.

As shown in FIG. 4A, the prism 4 of the optical functional sheet 1 has a concave or convex shape with a length ratio of 1.5 (bottom width 50 μm × 75 μm, height 25 μm). In the case of the substantially quadrangular pyramid, the area ratio of the light exit surfaces 4e, 4f, 4g, and 4h of the light emitted from the linear light source in the prism body 4 is 2: 1: 1: 2, If the arrangement direction (arrow 43) is not inclined with respect to the orientation direction (arrow 44) of the linear light source, the brightness (luminance) of the three virtual images in the optical functional sheet 1 that is expressed from one linear light source is It becomes almost equal.
However, when the virtual image in the optical functional sheet 1 expressed from another linear light source overlaps the virtual image in the optical functional sheet 1 expressed from one linear light source, the arrangement direction (arrow 43) of the prism bodies 4 is changed. The arrangement direction (arrow 43) of the prism bodies 4 is tilted with respect to the alignment direction (arrow 44) of the linear light source, rather than when it is not inclined with respect to the alignment direction (arrow 44) of the linear light source (FIG. 4B). The linear light source unevenness may be smaller when the light source is present (FIG. 4C).
Moreover, the length ratio of the bottom width in the shape of the prism body 4 of the optical functional sheet 1 is not limited to 1.5, and may be in the range of 1.0 to 5.0.

Further, as shown in FIG. 5, when the prism body 4 of the optical functional sheet 1 is a concave or convex quadrangular pyramid, the brightness of the virtual image in the optical functional sheet 1 developed from one linear light source. Are substantially equal, and the distance between adjacent virtual images in the optical functional sheet 1 expressed from one linear light source is substantially equal, so that the brightness of the virtual image in the optical functional sheet 1 expressed from a plurality of linear light sources is The arrangement direction (arrow 63) of the prism bodies 4 is the alignment direction of the linear light sources (arrow 63) so that the distances between adjacent virtual images in the optical functional sheet 1 expressed from a plurality of linear light sources are substantially equal. It is inclined 26.6 ° (= tan ⁻¹ (1/2)), which is considered to be theoretically most preferable with respect to the arrow 64). Thereby, while improving a light-diffusion function, without reducing a condensing function, a linear light source nonuniformity can be reduced.
Although FIG. 5 shows the case where the inclination angle between the arrangement direction of the prism bodies 4 (arrow 63) and the alignment direction of the linear light source (arrow 64) is 26.6 °, it is not limited to this. The distance between the linear light source and the optical functional sheet 1 is appropriately adjusted depending on the arrangement and type of the diffusion sheet, the diffusion plate, the reflection plate, and the like.
The area of each of the exit surfaces 4i, 4j, 4k, 4l, 4m is such that the ratio of the area of the exit surface 4i to the area of the exit surface 4m (area of the exit surface 4i / area of the exit surface 4m) is 0.25 to 0.25. 4 is preferably set, and it is more preferable that the areas of the exit surfaces 4i, 4j, 4k, 4l, and 4m are equal.
In addition, the prism shape is not limited to a flat shape (square pyramidal trapezoidal shape) as shown in FIG. 5, but may be a prism shape having a rounded top shape (rounded). Thereby, a light-diffusion function can be improved.

Further, as shown in FIG. 6, when the shape of the prism body 4 of the optical functional sheet 1 is a concave or convex substantially quadrangular pyramid (there is a gap between the quadrangular pyramids), one linear light source is used. The brightness of the virtual image in the expressed optical functional sheet 1 is substantially equal, and the distance between adjacent virtual images in the optical functional sheet 1 expressed from one linear light source is substantially equal, so that it is expressed from a plurality of linear light sources. The direction in which the prisms 4 are arranged so that the brightness of the virtual image in the optical functional sheet 1 is substantially equal, and the distance between adjacent virtual images in the optical functional sheet 1 expressed from a plurality of linear light sources is substantially equal. The arrow 73) is inclined by 26.6 ° (= tan ⁻¹ (1/2)), which is considered to be theoretically most preferable with respect to the alignment direction of the linear light source (arrow 74). Thereby, while improving a light-diffusion function, without reducing a condensing function, a linear light source nonuniformity can be reduced.
Although FIG. 6 shows the case where the inclination angle between the arrangement direction of the prism bodies 4 (arrow 73) and the alignment direction of the linear light source (arrow 74) is 26.6 °, it is not limited to this. The distance between the linear light source and the optical functional sheet 1 is appropriately adjusted depending on the arrangement and type of the diffusion sheet, the diffusion plate, the reflection plate, and the like.
In addition, the prism shape is not limited to a flat prismatic shape (substantially a quadrangular pyramid shape) as shown in FIG. 6, but may be a prism shape with a rounded pyramid apex (rounded). Thus, the light diffusion function can be improved.

In addition, as shown in FIG. 7, when the shape of the prism body 4 of the optical functional sheet 1 is a concave or convex substantially quadrangular pyramid (there is a gap between the quadrangular pyramids), the optical functional sheet 1 is expressed from one linear light source. The brightness of the virtual image in the optical functional sheet 1 is substantially equal, and the distance between adjacent virtual images in the optical functional sheet 1 expressed from one linear light source is substantially equal, so that a plurality of expressed from one linear light source. The direction in which the prisms 4 are arranged (arrow 83) so that the brightness of the virtual image in the optical functional sheet 1 expressed from the linear light source is substantially equal and the distance between adjacent virtual images in the optical functional sheet 1 is substantially equal. ) Is inclined by 26.6 ° (= tan ⁻¹ (1/2)), which is considered to be theoretically most preferable with respect to the alignment direction of the linear light source (arrow 84). Thereby, while improving a light-diffusion function, without reducing a condensing function, a linear light source nonuniformity can be reduced.
Although FIG. 7 shows the case where the inclination angle between the arrangement direction of the prism bodies 4 (arrow 83) and the alignment direction of the linear light source (arrow 84) is 26.6 °, it is not limited to this. The distance between the linear light source and the optical functional sheet 1 is appropriately adjusted depending on the arrangement and type of the diffusion sheet, the diffusion plate, the reflection plate, and the like.

The concept of the invention described above is also applied to the case where the prism body 4 of the optical functional sheet 1 has a concave or convex V groove.
For example, two prism sheets are stacked so that the V-groove directions are orthogonal to each other, and the angle between the V-groove direction of one of the prism sheets (the linear light source side) and the orientation direction of the cold cathode tube is 26.6 ° (= tan ⁻¹ (1/2)), it is theoretically preferable to arrange the optical functional sheet.
When two prism sheets are stacked so that the V-groove directions are orthogonal, the angle between the V-groove direction of one (linear light source side) prism sheet and the orientation direction of the cold cathode tube is X °, In the case of (90-X) °, an equivalent result is obtained.
Moreover, it is preferable that the apex angle of the shape in which the V-groove is formed is set to be 60 to 120 °.

  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 defined as the alignment direction of the linear light source.

  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.

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.
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.
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, the bottom width is 50 μm and the height is 25 μm under the conditions of 200 ° C. × 2 MPa × 10 min. A 17 cm square optical functional sheet (FIG. 3) onto which the concave regular quadrangular pyramid was transferred was obtained by hot pressing with a mold having a convex regular quadrangular pyramid. The obtained optical functional sheet, a cold cathode tube having a diameter of 3 mm as a plurality of linear light sources arranged in parallel, a reflector (light box) for reflecting light from the cold cathode tube, a cold cathode tube, A set of diffusion sheets (manufactured by Tsujiden Co., Ltd., D121Z) disposed between the optical functional sheets (FIG. 8), the arrangement direction of the prism bodies (regular quadrangular pyramids) and the alignment direction of the cold cathode tubes in the optical functional sheet A backlight unit was produced in which the optical functional sheet was rotated so that the angle was 7 ° (83 °). Here, the distance d between the cold cathode tube and the optical functional sheet is set to 17 mm, the distance D between the optical functional sheet and a color luminance meter described later is set to 350 mm, and the arrangement pitch p of the cold cathode tubes is set to 23 mm. The cold cathode tube is turned on, and the luminance in the optical functional sheet is measured with a color luminance meter (manufactured by Topcon Corporation, BM-7FAST) at regular intervals in the vertical direction from the cold cathode tube. While obtaining the average luminance value and the standard deviation of luminance between one pitch of the linear light sources up to immediately above the adjacent linear light source, the 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 10,021 cd, the standard luminance deviation is 57 cd, and the standard luminance deviation / average luminance value is The luminance unevenness evaluation was Δ (Table 1).
In an actual display, the diffusion degree is further increased by a diffusion plate or the like. However, in this embodiment, a diffusion plate or the like is used in order to emphasize the luminance unevenness and easily confirm the effect of reducing the luminance unevenness. Absent.

(Example 2)
Example 1 is the same as Example 1 except that the optical functional sheet is arranged so that the angle between the arrangement direction of the prism bodies (regular quadrangular pyramids) and the orientation direction of the cold cathode tubes in the optical functional sheet is 9 ° (81 °). A backlight unit was prepared and the luminance was measured. As a result, the luminance average value was 9,996 cd, the luminance standard deviation was 43 cd, the luminance standard deviation / luminance average value was 0.0043, and the luminance unevenness evaluation was ◯ (Table 1).

(Example 3)
Example 1 is the same as in Example 1 except that the optical functional sheet is disposed so that the angle between the arrangement direction of the prism bodies (regular quadrangular pyramids) and the orientation direction of the cold cathode tubes in the optical functional sheet is 11 ° (79 °). A backlight unit was prepared and the luminance was measured. As a result, the luminance average value was 10,052 cd, the luminance standard deviation was 26 cd, the luminance standard deviation / luminance average value was 0.0025, and the luminance unevenness evaluation was ◎ (Table 1).
In addition, an image taken from above the optical functional sheet is shown in FIG. 9, and a diffusion sheet (manufactured by Tsujiden Co., Ltd., D121Z) is not disposed between the cold cathode tube and the optical functional sheet in order to show a virtual image more clearly. An image is shown in FIG.

Example 4
Example 1 is the same as Example 1 except that the optical functional sheet is arranged so that the angle between the arrangement direction of the prism bodies (regular quadrangular pyramids) and the orientation direction of the cold cathode tubes in the optical functional sheet is 13 ° (77 °). A backlight unit was prepared and the luminance was measured. As a result, the luminance average value was 9,999 cd, the luminance standard deviation was 36 cd, the luminance standard deviation / luminance average value was 0.0036, and the luminance unevenness evaluation was ◯ (Table 1).

(Example 5)
Example 1 is the same as Example 1 except that the optical functional sheet is arranged so that the angle between the arrangement direction of the prism bodies (regular quadrangular pyramids) and the orientation direction of the cold cathode tubes in the optical functional sheet is 18 ° (72 °). A backlight unit was prepared and the luminance was measured. As a result, the luminance average value was 9,994 cd, the luminance standard deviation was 91 cd, the luminance standard deviation / luminance average value was 0.0091, and the luminance unevenness evaluation was Δ (Table 1).

(Example 6)
Example 1 except that the optical functional sheet was arranged so that the arrangement direction of the prism bodies (regular quadrangular pyramids) in the optical functional sheet and the alignment direction of the cold cathode tubes were parallel (inclination angle 0 ° (90 °)). A backlight unit was prepared in the same manner as described above, and the luminance was measured. As a result, the luminance average value was 10,074 cd, the luminance standard deviation was 85 cd, the luminance standard deviation / luminance average value was 0.0085, and the luminance unevenness evaluation was Δ (Table 1).
Further, an image taken from above the optical functional sheet is shown in FIG. 11, and a diffusion sheet (manufactured by Tsujiden Co., Ltd., D121Z) is not disposed between the cold cathode tube and the optical functional sheet in order to show a virtual image more clearly. An image is shown in FIG.

(Comparative Example 1)
Example 1 is the same as Example 1 except that the optical functional sheet is arranged so that the angle between the arrangement direction of the prism bodies (regular quadrangular pyramids) and the orientation direction of the cold cathode tubes in the optical functional sheet is 27 ° (63 °). A backlight unit was prepared and the luminance was measured. As a result, the luminance average value was 9,996 cd, the luminance standard deviation was 285 cd, the luminance standard deviation / luminance average value was 0.0285, and the luminance unevenness evaluation was x (Table 1).

  From the results of Examples 1 to 6 and Comparative Example 1, the angle between the arrangement direction of the prism bodies (regular quadrangular pyramids) and the orientation direction of the cold cathode tubes in the optical functional sheet is 0 to 18 ° (90 to 72 °), preferably Is 7 to 13 ° (83 to 77 °), and more preferably 11 ° (79 °), the luminance standard deviation / luminance average value is less than 0.0100, that is, an optical system developed from a plurality of linear light sources. It turned out that the brightness | luminance of the virtual image in a functional sheet is substantially equal, and the distance between the adjacent virtual images in the optical functional sheet expressed from the some linear light source can be made into substantially equal intervals.

(Example 7)
Instead of the optical functional sheet (FIG. 3) to which the concave regular square pyramid has been transferred, the optical functional sheet (FIG. 3) to which the concave substantially square pyramid having a length-to-short ratio of 1.5 (bottom width 50 μm × 75 μm, height 25 μm) has been transferred. Example 4) except that the optical functional sheet was arranged so that the angle between the arrangement direction of the prism bodies (substantially quadrangular pyramids) and the orientation direction of the cold cathode tubes was 70 ° in this optical functional sheet. A backlight unit was prepared in the same manner as described above, and the luminance was measured. As a result, the luminance average value was 10,005 cd, the luminance standard deviation was 48 cd, the luminance standard deviation / luminance average value was 0.0048, and the luminance unevenness evaluation was ◯ (Table 1).

(Example 8)
The backlight unit is the same as in Example 7 except that the optical functional sheet is arranged so that the angle between the arrangement direction of the prism bodies (substantially square pyramids) in the optical functional sheet and the orientation direction of the cold cathode tubes is 72 °. The brightness was measured. As a result, the luminance average value was 9,793 cd, the luminance standard deviation was 24 cd, the luminance standard deviation / luminance average value was 0.0024, and the luminance unevenness evaluation was ◎ (Table 1).
In addition, an image taken from above the optical functional sheet is shown in FIG. 13, and a diffusion sheet (manufactured by Tsujiden Co., Ltd., D121Z) is not disposed between the cold cathode tube and the optical functional sheet in order to show a virtual image more clearly. An image is shown in FIG.

Example 9
The backlight unit is the same as in Example 7 except that the optical functional sheet is arranged so that the angle between the arrangement direction of the prism bodies (substantially square pyramids) in the optical functional sheet and the orientation direction of the cold cathode tubes is 74 °. The brightness was measured. As a result, the luminance average value was 9,973 cd, the luminance standard deviation was 65 cd, the luminance standard deviation / luminance average value was 0.0065, and the luminance unevenness evaluation was ◯ (Table 1).

(Comparative Example 2)
Example 7 is the same as Example 7 except that the optical functional sheet is arranged so that the arrangement direction of the prism bodies (substantially square pyramids) in the optical functional sheet and the orientation direction of the cold cathode tubes are parallel (inclination angle 0 °). A backlight unit was prepared and the luminance was measured. As a result, the luminance average value was 10,157 cd, the luminance standard deviation was 149 cd, the luminance standard deviation / luminance average value was 0.0147, and the luminance unevenness evaluation was x (Table 1).

(Comparative Example 3)
The backlight unit is the same as in Example 7 except that the optical functional sheet is arranged so that the angle between the arrangement direction of the prism bodies (substantially quadrangular pyramids) in the optical functional sheet and the orientation direction of the cold cathode tubes is 63 °. The brightness was measured. As a result, the luminance average value was 9,916 cd, the luminance standard deviation was 181 cd, the luminance standard deviation / luminance average value was 0.0182, and the luminance unevenness evaluation was x (Table 1).

(Comparative Example 4)
The backlight unit is the same as in Example 7 except that the optical functional sheet is arranged so that the angle between the arrangement direction of the prism bodies (substantially square pyramids) in the optical functional sheet and the orientation direction of the cold cathode tubes is 81 °. The brightness was measured. As a result, the luminance average value was 9,844 cd, the luminance standard deviation was 186 cd, the luminance standard deviation / luminance average value was 0.0189, and the luminance unevenness evaluation was x (Table 1).

  From the results of Examples 7 to 9 and Comparative Examples 2 to 4, when the angle between the arrangement direction of the prism bodies and the orientation direction of the cold cathode tubes in the optical functional sheet is 70 to 74 °, preferably 72 °, the luminance standard The deviation / luminance average value is less than 0.0100, that is, the luminance of the virtual image in the optical functional sheet expressed from the plurality of linear light sources is substantially equal and adjacent in the optical functional sheet expressed from the plurality of linear light sources. It has been found that the distance between virtual images can be made to be approximately equal.

(Example 10)
Instead of the optical functional sheet (FIG. 3) to which the concave regular quadrangular pyramid is transferred, a prism sheet (RBEF manufactured by Sumitomo 3M Ltd.) having a V-groove is used, and the V-groove direction of the prism sheet and the orientation of the cold cathode tube A backlight unit was produced in the same manner as in Example 1 except that the optical functional sheet was disposed so that the angle with the direction was 63 °, and the luminance was measured. As a result, the luminance average value was 10,491 cd, the luminance standard deviation was 91 cd, the luminance standard deviation / luminance average value was 0.0087, and the luminance unevenness evaluation was Δ (Table 1).

(Example 11)
A backlight unit was produced in the same manner as in Example 10 except that the optical functional sheet was arranged so that the angle between the V-groove direction of the prism sheet and the orientation direction of the cold cathode tube was 64 °, and the luminance was measured. As a result, the luminance average value was 10,520 cd, the luminance standard deviation was 71 cd, the luminance standard deviation / luminance average value was 0.0068, and the luminance unevenness evaluation was Δ (Table 1).
Further, an image taken from above the optical functional sheet is shown in FIG. 15, and a diffusion sheet (manufactured by Tsujiden Co., Ltd., D121Z) is not disposed between the cold cathode tube and the optical functional sheet in order to show a virtual image more clearly. An image is shown in FIG.

(Example 12)
A backlight unit was produced in the same manner as in Example 10 except that the optical functional sheet was disposed so that the angle between the V-groove direction of the prism sheet and the orientation direction of the cold cathode tube was 65 °, and the luminance was measured. As a result, the luminance average value was 10,416 cd, the luminance standard deviation was 94 cd, the luminance standard deviation / luminance average value was 0.0090, and the luminance unevenness evaluation was Δ (Table 1).

(Comparative Example 5)
A backlight unit was prepared in the same manner as in Example 10 except that the optical functional sheet was arranged so that the V-groove direction of the prism sheet and the orientation direction of the cold cathode tube were parallel (inclination angle 0 °), and the luminance was increased. It was measured. As a result, the luminance average value was 11,176 cd, the luminance standard deviation was 521 cd, the luminance standard deviation / luminance average value was 0.0466, and the luminance unevenness evaluation was x (Table 1).
In addition, an image taken from above the optical functional sheet is shown in FIG. 17, and a diffusion sheet (manufactured by Tsujiden Co., Ltd., D121Z) is not disposed between the cold cathode tube and the optical functional sheet in order to show a virtual image more clearly. An image is shown in FIG.

(Comparative Example 6)
A backlight unit was produced in the same manner as in Example 10 except that the optical functional sheet was arranged so that the angle between the V-groove direction of the prism sheet and the orientation direction of the cold cathode tube was 59 °, and the luminance was measured. As a result, the luminance average value was 10,280 cd, the luminance standard deviation was 201 cd, the luminance standard deviation / luminance average value was 0.0195, and the luminance unevenness evaluation was x (Table 1).

(Comparative Example 7)
A backlight unit was prepared in the same manner as in Example 10 except that the optical functional sheet was arranged so that the angle between the V-groove direction of the prism sheet and the orientation direction of the cold cathode tube was 69 °, and the luminance was measured. As a result, the luminance average value was 10,384 cd, the luminance standard deviation was 164 cd, the luminance standard deviation / luminance average value was 0.0158, and the luminance unevenness evaluation was x (Table 1).

  From the results of Examples 10 to 12 and Comparative Examples 5 to 7, when the angle between the arrangement direction of the prism bodies and the orientation direction of the cold cathode tubes in the optical functional sheet is 63 to 65 °, preferably 64 °, the luminance standard The deviation / luminance average value is less than 0.0100, that is, the luminance of the virtual image in the optical functional sheet expressed from the plurality of linear light sources is substantially equal and adjacent in the optical functional sheet expressed from the plurality of linear light sources. It has been found that the distance between virtual images can be made to be approximately equal.

(Example 13)
Instead of the optical functional sheet (FIG. 3) to which the concave regular pyramid is transferred, two prism sheets (RBEF manufactured by Sumitomo 3M Limited) with V grooves are used, and the two prism sheets are arranged in the V groove direction. Other than arranging the optical functional sheets so as to be orthogonal to each other and the angle between the V-groove direction of the prism sheet on one side (linear light source side) and the orientation direction of the cold cathode tube is 30 ° (60 °) Manufactured a backlight unit in the same manner as in Example 1, and measured the luminance. As a result, the luminance average value was 11,917 cd, the luminance standard deviation was 104 cd, the luminance standard deviation / luminance average value was 0.0088, and the luminance unevenness evaluation was Δ (Table 1).

(Example 14)
The same as in Example 13 except that the optical functional sheet was arranged so that the angle between the V-groove direction of the prism sheet on one side (linear light source side) and the orientation direction of the cold cathode tube was 32 ° (58 °). A backlight unit was prepared and the luminance was measured. As a result, the luminance average value was 12,032 cd, the luminance standard deviation was 67 cd, the luminance standard deviation / luminance average value was 0.0055, and the luminance unevenness evaluation was Δ (Table 1).

(Example 15)
The same as in Example 13 except that the optical functional sheet is arranged so that the angle between the V-groove direction of the prism sheet on one side (linear light source side) and the orientation direction of the cold cathode tubes is 34 ° (56 °). A backlight unit was prepared and the luminance was measured. As a result, the luminance average value was 11,968 cd, the luminance standard deviation was 54 cd, the luminance standard deviation / luminance average value was 0.0046, and the luminance unevenness evaluation was ◯ (Table 1).

(Example 16)
The same as in Example 13 except that the optical functional sheet was arranged so that the angle between the V-groove direction of the prism sheet on one side (linear light source side) and the orientation direction of the cold cathode tube was 36 ° (54 °). A backlight unit was prepared and the luminance was measured. As a result, the luminance average value was 11,849 cd, the luminance standard deviation was 18 cd, the luminance standard deviation / luminance average value was 0.0015, and the luminance unevenness evaluation was ◎ (Table 1).
In addition, an image taken from above the optical functional sheet is shown in FIG. 19, and a diffusion sheet (manufactured by Tsujiden Co., Ltd., D121Z) is not disposed between the cold cathode tube and the optical functional sheet in order to show a virtual image more clearly. An image is shown in FIG.

(Example 17)
The backlight unit was mounted in the same manner as in Example 13 except that the optical functional sheet was arranged so that the angle between the V-groove direction of the prism sheet on one side (linear light source side) and the orientation direction of the cold cathode tube was 45 °. It produced and measured the brightness | luminance. As a result, the luminance average value was 11,981 cd, the luminance standard deviation was 26 cd, the luminance standard deviation / luminance average value was 0.0022, and the luminance unevenness evaluation was ◎ (Table 1).

(Comparative Example 8)
Example 13 except that the optical functional sheet is arranged so that the V groove direction of the prism sheet on one side (linear light source side) and the orientation direction of the cold cathode tube are parallel (inclination angle 0 ° (90 °)). A backlight unit was prepared in the same manner as described above, and the luminance was measured. As a result, the luminance average value was 12,047 cd, the luminance standard deviation was 120 cd, the luminance standard deviation / luminance average value was 0.0100, and the luminance unevenness evaluation was x (Table 1).
In addition, an image taken from above the optical functional sheet is shown in FIG. 21, and a diffusion sheet (manufactured by Tsujiden Co., Ltd., D121Z) is not disposed between the cold cathode tube and the optical functional sheet in order to show a virtual image more clearly. An image is shown in FIG.

(Comparative Example 9)
The same as in Example 13 except that the optical functional sheet was arranged so that the angle between the V-groove direction of the prism sheet on one side (linear light source side) and the orientation direction of the cold cathode tube was 27 ° (63 °). A backlight unit was prepared and the luminance was measured. As a result, the luminance average value was 11,928 cd, the luminance standard deviation was 141 cd, the luminance standard deviation / luminance average value was 0.0118, and the luminance unevenness evaluation was x (Table 1).

  From the results of Examples 13 to 17 and Comparative Examples 8 to 9, the angle between the arrangement direction of the prism bodies and the orientation direction of the cold cathode tubes in the optical functional sheet is 30 to 45 ° (60 to 45 °), preferably 36. When the angle is 54 (degrees), the brightness standard deviation / the brightness average value is less than 0.0100, that is, the brightness of the virtual image in the optical functional sheet expressed from a plurality of linear light sources is substantially equal, It has been found that the distance between adjacent virtual images can be made approximately equal.

(Reference Example 1)
Instead of the optical functional sheet (FIG. 3) to which the concave regular quadrangular pyramid is transferred, a prism sheet (RBEF manufactured by Sumitomo 3M Ltd.) having a V-groove is used, and the V-groove direction of the prism sheet and the orientation of the cold cathode tube An optical functional sheet is arranged so that the angle with respect to the direction is 0 °, and a backlight unit is produced in the same manner as in Example 1 except that a diffusion sheet (manufactured by Tsujiden Co., Ltd., D121Z) is not arranged, and luminance is measured. did. As a result, the luminance average value was 9,688 cd, the luminance standard deviation was 4,674 cd, the luminance standard deviation / luminance average value was 0.4825, and the luminance unevenness evaluation was x (Table 1).

(Reference Example 2)
A backlight unit was prepared and the luminance was measured in the same manner as in Reference Example 1 except that the optical functional sheet was arranged so that the angle between the V-groove direction of the prism sheet and the orientation direction of the cold cathode tube was 18 °. As a result, the luminance average value was 9,715 cd, the luminance standard deviation was 4,163 cd, the luminance standard deviation / luminance average value was 0.4285, and the luminance unevenness evaluation was x (Table 1).

(Reference Example 3)
A backlight unit was prepared and the luminance was measured in the same manner as in Reference Example 1 except that the optical functional sheet was arranged so that the angle between the V-groove direction of the prism sheet and the orientation direction of the cold cathode tube was 36 °. As a result, the luminance average value was 9,755 cd, the luminance standard deviation was 3,613 cd, the luminance standard deviation / luminance average value was 0.3704, and the luminance unevenness evaluation was x (Table 1).

(Reference Example 4)
A backlight unit was produced in the same manner as in Reference Example 1 except that the optical functional sheet was arranged so that the angle between the V-groove direction of the prism sheet and the orientation direction of the cold cathode tube was 54 °, and the luminance was measured. As a result, the luminance average value was 9,528 cd, the luminance standard deviation was 2,968 cd, the luminance standard deviation / luminance average value was 0.3115, and the luminance unevenness evaluation was x (Table 1).

(Reference Example 5)
A backlight unit was produced in the same manner as in Reference Example 1 except that the optical functional sheet was arranged so that the angle between the V-groove direction of the prism sheet and the orientation direction of the cold cathode tubes was 72 °, and the luminance was measured. As a result, the luminance average value was 9,206 cd, the luminance standard deviation was 3,264 cd, the luminance standard deviation / luminance average value was 0.3546, and the luminance unevenness evaluation was x (Table 1).

(Reference Example 6)
A backlight unit was prepared and the luminance was measured in the same manner as in Reference Example 1 except that the optical functional sheet was arranged so that the angle between the V-groove direction of the prism sheet and the orientation direction of the cold cathode tube was 90 °. As a result, the luminance average value was 9,253 cd, the luminance standard deviation was 5,380 cd, the luminance standard deviation / luminance average value was 0.5814, and the luminance unevenness evaluation was x (Table 1).

From the results of Reference Examples 1 to 6, when the angle between the arrangement direction of the prism bodies in the optical functional sheet and the orientation direction of the cold cathode tube is 54 to 72 °, the luminance standard deviation / luminance average value is 0 ° In comparison, it was found that the luminance standard deviation / luminance average value was small. That is, it was found that the luminance standard deviation / luminance average value shows substantially the same behavior regardless of whether or not a diffusion sheet (D121Z, manufactured by Tsujiden Co., Ltd.) is arranged.
However, when a diffusion sheet having a higher haze value than that of the above diffusion sheet (manufactured by Tsujiden Co., Ltd., D121Z) is used, or when a plurality of diffusion sheets are used, the optimum angle shifts in a direction away from 45 °. it is conceivable that. For example, when the optimum angle is 20 °, the optimum angle is 18 °, and when the optimum angle is 70 °, the optimum angle is 72 °.

FIG. 23 shows Example 6 (regular quadrangular pyramid (FIG. 3), inclination angle 0 °), Example 2 (regular quadrangular pyramid (FIG. 3), inclination angle 9 °), Example 3 (regular tetragonal pyramid (FIG. 3), inclination) FIG. 24 is a luminance distribution diagram in the optical functional sheet of Example 4 (regular quadrangular pyramid (FIG. 3), inclination angle 13 °), and FIG. 24 is Comparative Example 2 (regular quadrangular pyramid (FIG. 4), inclination angle 0 °), Example 7 (regular square pyramid (FIG. 4), inclination angle 70 °), Example 8 (regular square pyramid (FIG. 4), inclination angle 72 °), Example 9 (regular tetragonal pyramid (FIG. 4), inclination) 25 is a luminance distribution diagram in the optical functional sheet at an angle of 74 °, and FIG. 25 shows Comparative Example 5 (one V-groove, inclination angle 0 °), Example 10 (one V-groove, inclination angle 63 °), FIG. 26 is a luminance distribution diagram in the optical functional sheet of Example 11 (one V groove, inclination angle 64 °) and Example 12 (one V groove, inclination angle 65 °), and FIG. 26 shows Comparative Example 8 (V groove Like, the inclination angle of 0 °), Example 16 (V grooves 2 sheets, a luminance distribution diagram of the optical functional sheet tilt angle 36 °).
In each luminance distribution chart, the vertical axis represents luminance (cd / mm ² ), the horizontal axis represents position (distance from the reference point), and the linear light sources are 13.5 mm, 36.5 mm, 59.5 mm, Located at 82.5 mm.

From FIG. 23 to FIG. 26, the prism body in the optical functional sheet is more aligned than the case where the arrangement direction of the prism bodies in the optical functional sheet is not inclined with respect to the alignment direction of the linear light source (inclination angle 0 °). It has been found that when the arrangement direction is inclined by a predetermined inclination angle with respect to the alignment direction of the linear light source, the luminance distribution curve becomes flatter and luminance unevenness is suppressed.
Further, in the luminance distribution diagram showing the luminance distribution in the optical functional sheet, it is most preferable that there is no luminance peak, but for example, even when the luminance peak P exists as shown in FIG. In each of the regions R1 to R3 from the linear light source to the other linear light sources adjacent to the linear light source, approximately the same number of luminance peaks P having substantially the same height are present at substantially equal intervals, and the region R1. The interval from the rightmost luminance peak P of (region R2) to the leftmost luminance peak P of region R2 (region R3) is substantially equal to the interval of the luminance peak P in each of the regions R1 to R3. preferable.

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, the optical function sheet | seat can also be made into a reflecting plate by making the vertex angle of the optical function sheet | seat 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 (FIGS. 28 and 29).

FIG. 1 is a perspective view showing a configuration of an optical function sheet in a backlight unit of the present invention. FIG. 2 is a block diagram showing a configuration of a manufacturing apparatus used in the method for manufacturing the optical function sheet of FIG. FIG. 3A is a plan view showing an arrangement relationship between the linear light source and the optical functional sheet when the shape of the prism body of the optical functional sheet in FIG. 1 is a concave or convex regular quadrangular pyramid. FIG. 3B explains that when the brightness (brightness) of the virtual image in the optical functional sheet expressed from the linear light source is not constant, the distance from the adjacent virtual image is appropriately changed depending on the brightness (brightness) 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. 4A is a plan view showing the arrangement relationship between the linear light source and the optical functional sheet when the prism body of the optical functional sheet in FIG. 1 is a concave or convex substantially square pyramid with a length ratio of 1.5. FIG. FIG. 4B shows the case where the arrangement direction of the prisms of the substantially quadrangular pyramids is not inclined with respect to the alignment direction of the linear light source, and the extreme end of the virtual image developed from one linear light source and the other linear light sources. It is a figure which shows that the extreme end of the expressed virtual image has overlapped. FIG. 4C shows a virtual image expressed from one linear light source and a virtual image expressed from another linear light source in the case where the arrangement direction of the substantially quadrangular pyramid prism bodies is inclined with respect to the alignment direction of the linear light source. It is a figure which shows that and have overlapped moderately. FIG. 5 is a plan view showing an arrangement relationship between the linear light source and the optical functional sheet when the prism body of the optical functional sheet in FIG. 1 is a concave or convex truncated pyramid. FIG. 6 is a diagram showing an arrangement relationship between the linear light source and the optical functional sheet when the prism body of the optical functional sheet in FIG. 1 is a concave or convex substantially truncated pyramid. FIG. 7 is a diagram showing an arrangement relationship between the linear light source and the optical functional sheet when the shape of the prism body of the optical functional sheet in FIG. 1 is a concave or convex substantially quadrangular pyramid. FIG. 8 is a diagram showing the configuration of the backlight unit of the present invention. FIG. 9 is a photographed image of the optical functional sheet of Example 3. FIG. 10 is a photographed image of the optical functional sheet photographed under the same conditions except that the photographed image of FIG. 9 and the diffusion sheet are not arranged. FIG. 11 is a photographed image of the optical functional sheet of Example 6. FIG. 12 is a photographed image of the optical functional sheet photographed under the same conditions except that the photographed image of FIG. 11 and the diffusion sheet are not arranged. FIG. 13 is a photographed image of the optical functional sheet of Example 8. FIG. 14 is a photographed image of the optical functional sheet photographed under the same conditions except that the photographed image of FIG. 13 and the diffusion sheet are not arranged. FIG. 15 is a photographed image of the optical functional sheet of Example 11. FIG. 16 is a photographed image of the optical functional sheet photographed under the same conditions except that the photographed image of FIG. 16 and the diffusion sheet are not arranged. FIG. 17 is a photographed image of the optical functional sheet of Comparative Example 5. FIG. 18 is a photographed image of the optical functional sheet photographed under the same conditions except that the photographed image of FIG. 17 and the diffusion sheet are not arranged. FIG. 19 is a photographed image of the optical functional sheet of Example 16. FIG. 20 is a photographed image of the optical functional sheet photographed under the same conditions except that the photographed image of FIG. 19 and the diffusion sheet are not arranged. FIG. 21 is a photographed image of the optical functional sheet of Comparative Example 8. FIG. 22 is a photographed image of the optical functional sheet photographed under the same conditions except that the photographed image of FIG. 21 and the diffusion sheet are not arranged. FIG. 23 is a luminance distribution diagram in the optical functional sheets of Examples 2 to 4 and 6. 24 is a luminance distribution diagram in the optical functional sheets of Examples 7 to 9 and Comparative Example 2. FIG. FIG. 25 is a luminance distribution diagram in the optical functional sheets of Examples 10 to 12 and Comparative Example 5. FIG. 26 is a luminance distribution diagram in the optical functional sheets of Example 16 and Comparative Example 8. FIG. 27 is a diagram for explaining that the same number of luminance peaks P having substantially the same height exist at substantially equal intervals in the regions R1 to R3. FIG. 28 is a diagram for explaining moire. FIG. 29 is a diagram for explaining moire. FIG. 30 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 4a Output surface 4b Output surface 4c Output surface 4d Output surface 33 Arrow 34 Arrow

Claims (6)

A backlight unit comprising a plurality of linear light sources and an optical functional sheet in which a prism structure having a plurality of prism bodies is formed on at least one surface, and represents a luminance distribution in the optical functional sheet. In the luminance distribution diagram, the maximum luminance at the center of the backlight unit in the optical functional sheet is Bmax, the minimum luminance is Bmin, the peak position of the first virtual image expressed from the plurality of linear light sources is A ₁ , and the peak height It was the H ₁ of the second peak position of the virtual image 2 adjacent to the first virtual image a _2, a peak height and H _2, the n-1 adjacent to the virtual image of ... the n-2 a _n-1 and the peak position of the virtual image of _the peak height and H _n-1, the first n-1 of the n virtual image peak positions a _n of the adjacent virtual _image, the peak height was H _{n If, (H n-1} + _H ) / _(Backlight unit value of A _{n -A n-1)} is characterized in that a substantially constant.
However, the virtual image refers to a peak whose peak height H _n satisfies the condition of H _n ≧ 0.3 × (Bmax−Bmin), and in the luminance distribution diagram, the backlight unit includes a diffusion sheet and a diffusion plate. The luminance distribution in the optical function sheet when there is no sheet is shown.   The ratio of the peak height of one virtual image of a plurality of virtual images expressed from a plurality of linear light sources to the peak height of the virtual image adjacent to the one virtual image and the interval between the peak positions of the adjacent virtual images is approximately The backlight unit according to claim 1 which is equal.   In a backlight unit comprising a plurality of linear light sources and an optical functional sheet having a prism structure having a plurality of prism bodies on at least one surface thereof, the optical functional sheet expressed from the plurality of linear light sources The backlight unit is characterized in that the luminances of the virtual images in are substantially equal, and the distance between adjacent virtual images in the optical functional sheet is substantially equal. In the luminance distribution diagram showing the luminance distribution in the optical functional sheet, an area from a first linear light source of a plurality of linear light sources to a second linear light source adjacent to the first linear light source 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 is a region R ₂ ,... From the n−1th linear light source A region from the n-th linear light source to the n + 1-th linear light source is defined as a region R _n−1 , and a region from the n-th linear light source to the n + 1-th linear light source adjacent to the n-th linear light source. 4. The backlight unit according to claim 3, wherein when the region is the region R _n , approximately the same number of luminance peaks having substantially the same height are present at substantially equal intervals in each of the regions R _{1 to} R _n . In a backlight unit including a diffusion sheet, a region from a first linear light source among a plurality of linear light sources to a second linear light source adjacent to the first linear light source is defined as a region R ₁ , the first The region from the second linear light source to the third linear light source adjacent to the second linear light source is defined as an area R ₂ ,... From the (n−1) th linear light source to the nth linear light source. region R _n-1 the region from the linear light source of the n adjacent _to the region from the linear light source of the n to (n + 1) th linear light source which is adjacent to the linear light source of the first n and regions R _n Occasionally, the average value of the luminance of the optical functional sheet in the region R _n, claims 1 value obtained by dividing the standard deviation of the brightness in the optical functional sheet in the region R _n is less than 0.0100 4 The backlight unit according to any one of the above. The backlight unit according to claim 1, wherein the arrangement direction of the prism bodies is inclined with respect to the alignment direction of the linear light source.