JP2008282770A - Prism sheet and surface light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prism sheet capable of obtaining optical characteristics which could not be obtained by a conventional prism sheet, and to provide its manufacturing method. <P>SOLUTION: The prism sheet 1 is equipped with a flat sheet body 2, a prism part 6 arranged substantially on the whole single face of the sheet body, and a lens part 10 arranged at one part of the other face of the sheet body. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a prism sheet and a surface light source device including the prism sheet, and more specifically, a prism sheet in which a prism is formed on substantially the entire one surface and a lens is formed on at least one end of the other surface, and the prism. The present invention relates to a surface light source device including a sheet.

  A prism sheet, which is an optical sheet having prism-like uneven portions formed on the surface thereof, is used in a backlight mechanism or the like of a liquid crystal display device.

  With the downsizing and thinning of electronic devices such as mobile phones on which liquid crystal display devices are mounted, there is a demand for downsizing and thinning of liquid crystal display devices themselves. In order to meet such demands, higher optical performance has been demanded for prism sheets used in backlight mechanisms.

For example, in an end-face incident type backlight mechanism in which LED chips are arranged on the end face of the light guide plate, the light from the light guide plate is efficiently oriented in the front direction on the prism sheet placed above the light guide plate to increase the brightness. In addition to the function to perform, new brightness prevention such as uneven brightness in which bright and dark portions occur in the vicinity of the region where the LEDs are arranged (light incident portion) and oblique bright lines that are visible in perspective observation from the side opposite to the light source are prevented. Function is required.
In addition, in a backlight mechanism using a cold cathode tube lamp (CCFL), prevention of CCFL reflection bright lines is required. In particular, when the light guide plate is thinned, it is required to prevent luminance unevenness that becomes large at the light incident portion.
Patent Document 1 proposes a backlight unit that solves these problems, but the above-described technique does not solve the problem of the perspective bright line of the light incident portion, and the so-called frame portion is narrowed (narrow). There was a problem that the level of uniformity (in the picture frame) was insufficient.

JP 2005-142078 A

  The present invention has been made to solve such problems, and provides a prism sheet, a surface light source device, and a prism sheet manufacturing method capable of obtaining optical performance that cannot be obtained by a conventional prism sheet. The purpose is that.

  According to the present invention, a flat sheet main body, a prism portion composed of a plurality of prisms arranged on substantially the entire one surface of the sheet main body, and at least one end of the other surface of the sheet main body are arranged. And a lens portion composed of a plurality of columnar lenses extending substantially parallel to the direction in which the prism extends, and the lens portion has an interval between the lenses in a direction orthogonal to the direction in which the lens extends. There is provided a prism sheet characterized by being arranged so as to increase from one end to the other end of the sheet body.

  According to such a configuration, the optical performance that could not be obtained with the conventional prism sheet due to the synergistic effect of the prism portion arranged on one surface of the sheet body and the lens portion arranged on the other surface. can get. That is, since the distance between the lenses in the direction orthogonal to the direction in which the lenses extend is increased from one end of the sheet body toward the other end, in the sheet body of the portion where both the prism portion and the lens portion are formed. Generation of moire can be suppressed. Therefore, for example, if the lens unit is disposed in the vicinity of the light incident part, it is possible to effectively prevent luminance unevenness in the light incident part.

According to another preferred aspect of the present invention, the lens portion is formed such that the height of the lens decreases from one end of the sheet body toward the other end. Here, the decrease in height means that the length of the lens in the vertical direction (the thickness direction of the prism sheet) is shortened.
According to another preferred aspect of the present invention, the lens portion is formed such that the width of the lens decreases from one end of the sheet body toward the other end.

  According to another preferred aspect of the present invention, the lens portion is composed of a plurality of protrusions having a substantially triangular, semi-circular, semi-elliptical, or substantially trapezoidal cross section.

  According to another preferred aspect of the present invention, the prism portion is composed of a plurality of substantially triangular prism portions.

According to another preferable aspect of the present invention, at least a side surface or a valley portion of the lens portion is roughened.
According to another preferable aspect of the present invention, at least a side surface or a valley portion of at least a prism portion located below the lens portion is roughened.
According to another preferred aspect of the present invention, at least a side surface of at least a prism portion located below the lens portion is roughened or a trough portion is deformed.

According to another preferred aspect of the present invention, a part or the whole of the surface other than the lens part is roughened on the surface on which the lens part is disposed.
According to another preferable aspect of the present invention, the roughening is performed by regularly arranging concave shapes or convex shapes, or an assembly in which concave shapes or convex shapes are randomly arranged inside. It is made by arranging regularly.
According to another preferred aspect of the present invention, on the surface on which the lens portion is disposed, a part or all of the surface other than the lens portion is formed with fine and random irregularities by blasting or the like. .

According to another preferred embodiment of the present invention, a diffusion material having an average particle diameter of 4 μm to 10 μm is mixed and dispersed inside the sheet body.
According to another preferred embodiment of the present invention, a resin containing a diffusion material having an average particle diameter of 4 μm to 10 μm is coated on at least one surface of the sheet body.

  According to another aspect of the present invention, a light source plate having a primary light source, a light incident surface for entering light emitted from the primary light source, and a light exit surface for emitting incident light, and the light emission of the light guide plate There is provided a surface light source device comprising the above-described prism sheet disposed to face a surface.

  According to another preferred aspect of the present invention, the light incident surface is a side end surface of the light guide plate, and the light guide plate has a predetermined length from the light incident surface over the predetermined length. The prism sheet is disposed at a position farther from the light incident surface than the light incident portion.

According to another preferred aspect of the present invention, the light incident portion is formed such that the thickness gradually decreases in a direction away from the light incident surface.
According to the other preferable aspect of this invention, the thickness of the said light-guide plate in the said light-incidence surface is 500 micrometers or less.
According to the other preferable aspect of this invention, the said predetermined dimension in which the said light-incidence part is formed is 0.5 mm or more and 4 mm or less.
According to another preferred aspect of the present invention, the primary light source is an LED light source.

  According to another preferred embodiment of the present invention, the apex angle of the lens portion is 70 to 120 degrees, preferably 80 to 110 degrees, and more preferably 80 to 100 degrees.

  According to another preferred embodiment of the present invention, the substantially triangular prism-shaped prism portion has an apex angle of 40 to 90 degrees, preferably 45 to 70 degrees.

  According to another preferable aspect of the present invention, the pitch of the prisms constituting the prism portion is 1 μm to 60 μm, preferably 10 μm to 30 μm, and more preferably 15 μm to 20 μm.

  According to the present invention having such a configuration, it is possible to obtain optical performance that could not be obtained with a conventional prism sheet in the vicinity of a light incident portion such as a CCFL or a chip-type LED.

Hereinafter, a configuration of a prism sheet 1 according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.
[First embodiment]
FIG. 1 is a schematic plan view showing the configuration of the prism sheet 1 according to the first embodiment of the present invention, and FIG. 2 is a schematic side view. In each drawing, prisms and protrusions are exaggerated.

  As shown in FIGS. 1 and 2, the prism sheet 1 is a substantially rectangular sheet member formed of a transparent energy ray curable resin, and includes a flat sheet body 2. In the present embodiment, the sheet body 2 has a rectangular shape with a width of 36.6 mm and a length of 48.8 mm. The thickness of the sheet body is preferably 300 μm or less, more preferably 100 μm or less, and most preferably 50 μm or less.

  The entire back surface of the sheet body 2 is provided with a prism portion 6 composed of a number of substantially triangular prisms 4 arranged in parallel so as to extend in the width direction of the sheet body 2. A lens portion 10 composed of a plurality of substantially triangular prism-shaped protrusions 8 arranged in parallel is provided on one end side in the longitudinal direction of the surface of the sheet body 2. The sheet body 2, the prism 4 and the protrusion 8 are all made of a transparent resin.

  In the prism sheet 1 of this embodiment, the apex angle α of each triangular prism 4 is preferably 40 to 90 degrees, and more preferably 45 to 70 degrees. If the apex angle is less than 40 degrees, the tip is likely to be deformed, and it becomes difficult to form a mold for forming the prism 4, which is not preferable. On the other hand, if it is larger than 90 degrees, the efficiency of deflecting light in the normal direction is lowered, which is not preferable. Furthermore, in the lens sheet 1, the pitch of the prisms 4 is 1 μm to 60 μm, preferably 10 μm to 30 μm, and more preferably 15 μm to 20 μm.

  Here, the prism 4 may be disposed so as to extend at a predetermined angle with respect to the width direction of the sheet body 2 in order to suppress the occurrence of moire. The predetermined angle is preferably in the range of 0 ° to 6 °. Further, in order to prevent wear between the light guide plate used together with the prism sheet 1 and the apex of the prism 4, the tip of the prism 4 may be cut into a flat and minute shape. The width of this fine cut is preferably 2 μm or less, more preferably 1 μm or less, and most preferably 0.5 μm or less. If the fine cut width is too wide, the light guide plate and the fine cut portion may cause optical contact, and the optical contact portion may be visually recognized as an optical defect on the backlight, or the luminance may be reduced. Therefore, the above range is preferable.

In the prism sheet 1 of the present embodiment, the substantially triangular prism-shaped protrusion 8 extends substantially along the width direction of the sheet body 2. With this arrangement of the prism 4 and the protrusion 8, the ridge line of the protrusion 8 extends substantially parallel to the ridge line of the prism 4.
The protrusions 8 may be arranged to extend at a predetermined angle with respect to the width direction of the sheet body 2 in order to suppress the occurrence of moire. The predetermined angle is preferably in the range of 0 ° to 6 °.
Therefore, the angle formed by the direction in which the prism 4 extends and the direction in which the protrusion 8 extends is preferably in the range of 0 ° to 12 °.

  Further, the protrusions 8 are arranged so that the interval gradually increases from one end of the sheet body 2 toward the other end. In the present embodiment, the distance between the ridge lines of the protrusions 8 in the direction orthogonal to the direction in which the protrusions 8 extend, that is, the pitch P of the protrusions 8 increases from one end to the other end of the sheet body 2 at a constant increase rate. With such an arrangement, moire generated due to the combination with the prism 4 can be more effectively suppressed.

  The prism sheet 1 of the present embodiment is a prism sheet used for a 2.4-inch LED backlight for mobile phones, and the protrusions 8 are formed over a range of about 7 mm from the end of the prism sheet 1. This length is preferably 15 mm or less, more preferably 10 mm or less, and even more preferably 7 mm or less. Moreover, it is preferable that the protrusion 8 is formed over the range from 0.5 to 30 times the thickness of the light entrance part of the light guide plate to be used from one end of the sheet body 2.

  The apex angle β of each protrusion 8 is preferably in the range of 70 to 120 degrees, more preferably 80 to 110 degrees, still more preferably 80 to 100 degrees, and most preferably about 90 degrees.

In the prism sheet of the present embodiment, the side surfaces or valleys of the protrusions 8 are roughened.
Further, the portion of the surface of the sheet body 2 where the protrusions 8 are not formed is also roughened. The degree of roughening is weak. Such roughening makes it difficult to visually recognize the boundary between the protrusion 8 and other portions, and further prevents sticking with the liquid crystal panel placed immediately above when constructing the backlight. The roughening may be applied with gradation so that the degree of roughening gradually decreases from the side where the protrusions 8 are provided toward the other end.
Furthermore, the troughs or side surfaces of the prism 4 located below the protrusions 8 are also roughened.

When such a prism sheet 1 is manufactured, the prism 4 and the protrusion 8 may be formed on both surfaces of the sheet body 2 by injection molding. In this case, first, a mold having a shape corresponding to the shape of the prism section 6 and the lens section 10 is prepared, and energy ray curable resin is injected into the mold. Thereafter, it is preferable to integrally form the sheet body 2, the prism portion 6, and the lens portion 10 by irradiating the energy ray curable resin with an energy ray and curing it.
In addition, you may obtain the prism sheet 1 by forming the lens part 10 which consists of several protrusion 8 by injection molding etc. in the other surface of the sheet | seat in which the prism 4 is formed in one surface.

  When the prism sheet 1 described above is manufactured, the prisms 4 and the protrusions 6 are formed on both surfaces of the sheet body 2 by using roller dies having shapes corresponding to the shapes of the prism part 4 and the protrusions 8, respectively. It may be produced by transferring. In this case, first, the sheet body 2 is wound around a roller mold for forming the prism portion 4, and an energy curable resin is injected between the sheet body 2 and the roller mold. And the prism part 6 is continuously formed in the single side | surface of the sheet | seat main body 2 by irradiating an energy ray to an energy ray hardening resin and making it harden | cure. Further, the surface opposite to the prism portion 6 of the sheet body 2 is wound so as to face the roller mold for forming the lens section 10, and an energy ray curable resin is injected between the sheet body 2 and the roller mold. Then, it is cured by irradiating energy rays. Thereby, the prism part 6 and the lens part 10 can be formed on both surfaces of the sheet body 2.

Here, in the present embodiment, a thin prism sheet is required as a backlight for mobile phones. The thickness of this type of prism sheet is preferably 20 to 100 μm, and more preferably 30 to 65 μm. 40 to 50 μm is most preferable. If the thickness is reduced, the sheet strength may be impaired or the productivity may be lowered. For example, a resin having a high Tg or a resin having a high strength is used as a raw material.
Although the raw material of the energy ray curable resin used as the material of the prism sheet 1 of this embodiment will not be specifically limited if the predetermined | prescribed optical performance is exhibited, For example, the following material is mentioned.

A resin raw material 1 which is a rigid component and represented by Chemical Formula 1.

Resin raw material 2 which is a rigid component and represented by Chemical Formula 2.

Resin raw material 3 which is a flexible component and represented by Chemical Formula 3.

Resin raw material 4 which is a flexible component and is represented by Chemical Formula 4.

Resin raw material 5 which is a flexible component and represented by Chemical Formula 5.

Resin raw material 6 represented by Chemical Formula 6 which is a flexible component.

A polymerization initiator 7 for UV curing represented by Chemical Formula 7.

  Resin raw material 8 represented by chemical formula 24:

  A resin raw material 9 which is a rigid component and has a structure in which an aromatic ring of the resin raw material 5 is hydrogenated.

A resin raw material 10 which is a rigid component and is a urethane acrylate mixture containing the following components A and B.
Component A: Mixture of hexamethylene diisocyanate and trimer of hexamethylene diisocyanate Component B: Mixture of hydroxypropyl acrylate and pentaerythritol triacrylate

  In the present invention, the produced polymer has a glass transition temperature (Tg) of 40 ° C. or higher, preferably 60 ° C. or higher, more preferably 80 ° C. or higher.

  Examples of the raw material for producing such a polymer include those represented by the following chemical formulas 8 to 25.

ビスフェノールＡＥＯ変性（ｎ＝２）ジアクリレート

Bisphenol AEO modified (n = 2) diacrylate

イソシアヌル酸ＥＯ変性ジアクリレート

Isocyanuric acid EO-modified diacrylate

トリプロピレングリコールジアクリレート

Tripropylene glycol diacrylate

テトラエチレングリコールジアクリレート

Tetraethylene glycol diacrylate

ペンタエリスリトールトリアクリレート

Pentaerythritol triacrylate

トリメチロールプロパントリアクリレート

Trimethylolpropane triacrylate

トリメチロールプロパンＰＯ変性（ｎ＝１）トリアクリレート

Trimethylolpropane PO modified (n = 1) triacrylate

イソシアヌール酸ＥＯ変性トリアクリレート

Isocyanuric acid EO-modified triacrylate

ｎ＝２
トリメチロールプロパンＰＯ変性（ｎ＝２）トリアクリレート

トリメチロールプロパンＥＯ変性（ｎ＝２）トリアクリレート

n = 2
Trimethylolpropane PO modified (n = 2) triacrylate

Trimethylolpropane EO modified (n = 2) triacrylate

Ｒ：Ｈまたは−ＣＯ−ＣＨ＝ＣＨ２
ジペンタエリスリトールペンタ及びヘキサアクリレート

R: H or -CO-CH = CH2
Dipentaerythritol penta and hexaacrylate

ペンタエリスリトールテトラアクリレート

Pentaerythritol tetraacrylate

Ａ：アクリル酸
Ｘ：多価アルコール
Ｙ：多塩基酸
ｎ：１〜１０

A: Acrylic acid X: Polyhydric alcohol Y: Polybasic acid n: 1 to 10

トリメチロールプロパンアクリル酸安息香酸エステル

Trimethylolpropane acrylic acid benzoate

ビスフェノールＡのＥＯ付加物ジアクリレート

Bisphenol A EO adduct diacrylate

ビスフェノールＡのＰＯ付加物ジアクリレート

PO adduct diacrylate of bisphenol A

  Further, as the energy ray curable resin component, at least a polymer having a glass transition temperature (Tg) of 40 ° C. or higher, preferably 70 ° C. or higher, more preferably 90 ° C. or higher, most preferably 110 ° C. or higher is used. The

  Further, when at least trifunctional acrylate is used as a component of the energy ray curable resin, the polymerization curing reaction is fast, the rigidity of the film is increased, and Tg is also increased.

When an acrylate monomer having two or more, preferably 3 to 6, acryloyl groups in the molecule is used, the polymerization and curing reaction is fast, and the rigidity and Tg of the film are increased.
Inclusion of an alicyclic bifunctional acrylate in the molecule increases the rigidity and Tg of the film.

  When an epoxy acrylate is included, it is less susceptible to oxygen inhibition during curing and has excellent adhesion to metal. Conveniently, a polymer is taken in the metal mold, and it is difficult to adhere to the glass / transparent resin when the mold is opened, and the peeling direction is always the metal mold surface. Peeling from the metal surface is performed with a blow.

Urethane acrylate and imide acrylate may be used as the diluent.
(A hexamethylene diisocyanate / hexamethylene diisocyanate trimer mixture) and / or a urethane acrylate comprising the components (hydroxypropyl acrylate / pentaerythritol triacrylate mixture) A rate mixture may be used.

As the photopolymerization initiator, a polymerization initiator for UV curing may be used in combination with a sensitizer and polymerized using an energy sensitization reaction. The photosensitive wavelength is extended to improve deep curing.
For example, ITX (2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one and Irgacure907 initiator: Ciba Specialty Chemicals Co., Ltd. may be used in combination.

When a photopolymerization initiator having an absorption peak in a long wavelength region of 360 nm or longer is used as the UV curing polymerization initiator, the photosensitive wavelength is increased and deep curing is improved.
Examples thereof include BAPO {bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide} and MBAPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide).

In addition, if a photopolymerization initiator having photo-fading properties is used as a UV curing polymerization initiator, the absorption band of the UV curing polymerization initiator disappears along with the photoreaction, and the light reaches the deep part and cures deeply. Advances.
Examples of photopolymerization initiators having photo-fading properties include acylphosphine oxides such as MBAPO (2,4,6-trimethylbenzoyl-diphenylphosphine oxide), and bis (η5-2,4-cyclopentadiene-1- Yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) -phenyl) titanium, OXE ({1,2-octanedione, 1- [4- And oxime esters such as (phenylthio)-, 2- (O-benzoyloxime)]}).

When a photopolymerization initiator that can be used in irradiation with visible light energy rays is used, polymerization can be started by irradiation with visible light, so that a laser can be used as an energy ray source.
For example, titanocene initiators such as bis (η5-2,4-cyclopentadien-1-yl) -bis (2,6-difluoro-3- (1H-pyrrol-1-yl) -phenyl) are listed. It is done.

  Specific examples of the energy beam curable resin are as follows.

Example 1
Resin material 1 (40 wt%) + Resin material 2 (20 wt%) + Resin material 3 (40 wt%) + UV
Curing polymerization initiator 7 for curing (1.2 wt%)
A cured product having a Tg of 120 ° C. was obtained.

(Example 2)
Resin material 10 (45 wt%) + resin material 3 (30 wt%) + resin material 5 (25 wt%) + UV curing polymerization initiator 7 (1.2 wt%) is cured,
A cured product having a Tg of 70 ° C. was obtained.

Next, the surface light source device 12 using such a prism sheet 1 will be described. FIG. 3 is a side view of the surface light source device 12 configured using the prism sheet 1 of the present embodiment.
The surface light source device 12 is arranged at a predetermined interval opposite to the prism sheet 1, the light guide plate 14 arranged to face the surface of the prism sheet 1 on which the prism 4 is formed, and the end face of the light guide plate 14. And a plurality of LED light sources 16 as primary light sources.

  A side end surface of the light guide plate 14 facing the LED light source 16 is a light incident surface 18 on which light from the LED light source 16 is incident. Further, the upper surface of the light guide plate 14 facing the prism sheet 1 serves as a light emitting surface 20 that guides and emits light from the LED light source 16. In the light guide plate 14, a reflection sheet 22 is provided on the lower surface opposite to the light emitting surface 20.

The light guide plate 14 includes a light incident portion 24 that has a predetermined length L from the light incident surface 18 and a thickness of the light guide plate 14, that is, a length in a direction perpendicular to the light emitting surface 20, which is larger than the other portions.
FIG. 4 shows an enlarged view of the light incident portion 24. As shown in FIG. 4, the upper surface of the light incident portion 24 is an inclined surface 26 such that the thickness of the light guide plate 14 decreases as the distance from the light incident surface 18 increases. The prism sheet 1 is disposed on the light emitting surface 20 at a position farther from the light incident surface 18 than the light incident portion 24. In the case where the surface light source device 12 is used as a liquid crystal panel such as a personal computer or a mobile phone, the light incident portion 24 may be disposed outside the display portion in a so-called frame.

Here, the thickness H of the light incident portion 24 on the light incident surface 18 is preferably 500 μm or less. By setting the thickness H to 500 μm or less, the surface light source device 12 can be made thinner.
Moreover, the predetermined length L from the light-incidence surface 18 of the light-incidence part 24 is 0.5 mm or more and 4 mm or less, Preferably they are 1.0 mm or more and 2.5 mm or less, More preferably, they are 1.5 mm or more and 2 mm or less. By making the predetermined dimension L larger than 0.5 mm, the inclination angle of the inclined surface 26 can be moderated, and light leakage at the light incident portion 24 can be suppressed. In addition, by making the predetermined dimension L smaller than 4 mm, the area on which the prism sheet 1 is placed can be increased, and thus the display area of the surface light source device 12 can be increased.

  Furthermore, the angle δ formed by the inclined surface 26 of the light incident portion 24 and the light emitting surface 20 is preferably 45 degrees or less. If the angle δ is 45 degrees or more, the inclined surface 26 is steeply inclined, so that light leakage at the light incident portion 24 becomes severe.

  In the surface light source device 12 having such a configuration, when the light guide plate 14 is thinned and the light incident portion 24 is provided, the light emitted from the LED light source 16 and passed through the light incident portion 24 is the prism 4 of the prism sheet 1. And totally deviate in the normal direction of the prism sheet 1 to cause local bright portions. In the surface light source device 12 of the present invention, the light deviated in the normal direction of the prism sheet 1 by the prism 4 is totally reflected by the protrusions 8 and partly recycled to the light guide plate 14. The recycled light is mixed with the light guided in the light guide plate 14 in the light guide plate 14 and emitted from the light exit surface 20. Since the projection 8 is provided on a part on the light source side of the other surface where the prism portion of the prism sheet 1 is disposed, it is possible to reliably prevent the bright portion in the vicinity of the light incident surface 18 and light. The luminance at a position away from the incident surface 18 can be improved. Further, the obliquely incident light emitted from the LED light source 16 and deviated from the normal direction of the light incident surface 18 is refracted by the protrusion 8 and is efficiently deflected in the normal direction of the prism sheet 1. Therefore, the oblique bright lines in the perspective can be eliminated and the dark area (frame) between the LEDs can be reduced.

Since the pitch P of the projections 8 of the lens unit 10 is gradually increased, even when the projections 8 extend substantially parallel to the direction in which the prism 4 extends, moire generated in the prism sheet 1 can be satisfactorily suppressed. . In order to conceal the defect, the pitch P of the protrusions 8 of the lens unit 10 is preferably 200 μm or less.
Further, since the valleys or side surfaces of the prisms 4 disposed on the side surfaces and valleys of the protrusions 8 and the back surface side of the protrusions 8 are roughened, the concealment of optical defects is enhanced by the scattering effect, A high-luminance and high-quality backlight can be configured.
Moreover, since the prism sheet 1 is not arranged on the upper part of the light incident part 24 but is arranged at a position away from the light incident surface 18 by a predetermined distance so as not to overlap the light incident part 24, the luminance of the surface light source device 12 is improved. Thus, it is possible to promote thinning.

[Second Embodiment]
Next, a prism sheet according to a second embodiment of the present invention will be described. The prism sheet of the second embodiment has substantially the same configuration as the prism sheet 1 of the first embodiment except that the shape and arrangement of the protrusions 8 of the prism sheet 1 according to the first embodiment are different.

  FIG. 5 shows a side view of the prism sheet 30 according to the second embodiment of the present invention. As shown in FIG. 5, the lens portion 32 of the prism sheet 30 includes a plurality of protrusions 34. These protrusions 34 are formed in a triangular prism shape having a triangular cross section like the protrusions 8 of the first embodiment, and extend substantially along the width direction of the sheet body 2. The length of one side of the cross-sectional triangle of the protrusion 34 gradually decreases from one end of the sheet body 2 toward the other end. Therefore, the height and width of the protrusion 34 are formed so as to gradually decrease from one end of the sheet body 2 toward the other end. Note that the pitch P of the protrusions 34 increases from one end of the sheet body 2 toward the other end at a constant increase rate, like the protrusions 8 of the first embodiment.

  Even in the prism sheet 30 of the second embodiment having such a configuration, the occurrence of moire can be satisfactorily suppressed as in the prism sheet 1 of the first embodiment.

[Third embodiment]
Next, a prism sheet according to a third embodiment of the present invention will be described. The prism sheet of the third embodiment has substantially the same configuration as the prism sheet 1 of the first embodiment, except that the shape and arrangement of the protrusions 8 of the prism sheet 1 of the first embodiment are different.

  FIG. 6 shows a side view of the prism sheet 40 according to the third embodiment. As shown in FIG. 6, the lens portion 42 of the prism sheet 40 is configured by arranging a plurality of protrusions 44 substantially along the width direction of the sheet body 2. The lens portion 42 has a plurality of protrusions 44 having the same cross-sectional dimension (three in FIG. 6) arranged, and the length of one side of the cross-sectional triangle is plural from one end to the other end of the sheet body 2. It is getting smaller step by step. Accordingly, the height and width of the protrusion 44 are formed so as to decrease stepwise from one end of the sheet body 2 to the other end. The pitch P of the protrusions 44 is equal between the protrusions 44 having the same cross-sectional dimension, but the pitch P is set to be large between the protrusions 44 whose cross-sectional dimensions are reduced. Therefore, the pitch P between the protrusions 44 is gradually reduced from one end of the sheet body 2 toward the other end.

  Even in the prism sheet 40 of the third embodiment having such a configuration, the occurrence of moire can be satisfactorily suppressed as in the prism sheet 1 of the first embodiment.

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention.
For example, the shape of the protrusion is not limited to a columnar shape with a triangular cross section, and the cross section may be a substantially semicircular shape like the protrusion 50 shown in FIG. Alternatively, the shape of the protrusion may be substantially trapezoidal in cross section like the protrusion 60 shown in FIG.

The height and width of the protrusions may be reduced stepwise as in the second embodiment, and gradually and continuously at a constant reduction rate from one end of the sheet body to the other end as in the second embodiment. May be reduced. Further, the height and width of the protrusions may be reduced at different reduction rates.
The interval between the protrusions may be gradually increased as in the first embodiment and the second embodiment, or may be increased step by step for each plurality as in the third embodiment. Further, the interval between the protrusions may gradually increase at different increasing rates. Furthermore, the arrangement of the protrusions may be configured such that, for example, the height and width of the protrusions are decreased step by step, and the interval between the protrusions is gradually increased at a constant increase rate. .

  The lens portion is formed at one end of the prism sheet. However, the present invention is not limited to this, and for example, when a primary light source such as an LED light source is disposed at both ends of the prism sheet, the lens portion is formed at both ends of the prism sheet. May be. In short, the lens part should just be formed in the at least one end part of the prism sheet.

  The prism sheet is a base film in which a diffusing material having an average particle size of 4 to 10 μm is mixed and dispersed, or a resin containing such a diffusing material is applied to at least one surface by solution application or (multilayer) extrusion, etc. Defect concealment may be enhanced using the base film coated in step (b). When the particle size of the diffusing material is smaller than 4 μm, the defect concealing effect is low, and when it is larger than 10 μm, speckle (glare) becomes strong, so the above range is preferable.

When forming the prism portion or the lens portion of the prism sheet using the energy beam curable resin, in order to improve the mold release of the energy beam curable resin from the mold, a release agent is appropriately added to the energy beam curable resin. It is preferable to contain.
The primary light source is not limited to an LED light source, and any type of light source can be used.

It is a typical top view of a part of prism sheet of a first embodiment of the present invention. It is a typical side view of the prism sheet of FIG. It is a side view of the surface light source device comprised using the prism sheet of FIG. It is drawing which expands and shows a part of light-guide plate. It is a typical side view which shows a part of prism sheet of 2nd embodiment of this invention. It is a typical side view which shows a part of prism sheet of 3rd embodiment of this invention. It is a typical side view which shows a part of modification of a prism sheet. It is a typical side view which shows a part of another modification of a prism sheet.

Explanation of symbols

1, 30, 40: Prism sheet 4: Prism 6: Prism portions 8, 34, 44, 50, 60: Protrusions 10, 32, 42: Lens portion 12: Surface light source device 14: Light guide plate 24: Light incident portion

Claims (9)

A flat sheet body,
A prism portion composed of a plurality of prisms disposed on substantially the entire one surface of the sheet body;
A lens unit that is arranged at least at one end of the other surface of the sheet body and includes a plurality of columnar lenses extending substantially parallel to the direction in which the prism extends;
The lens portion is arranged so that an interval between the lenses in a direction orthogonal to a direction in which the lens extends increases from one end of the sheet body toward the other end.
A prism sheet characterized by that. The lens portion is formed such that the height of the lens decreases from one end of the sheet body toward the other end.
The prism sheet according to claim 1. The lens portion is formed such that the width of the lens decreases from one end of the sheet body toward the other end.
The prism sheet according to claim 1 or 2. At least a side surface or a valley portion of the lens is roughened,
The prism sheet according to any one of claims 1 to 3. In the surface where the lens unit is arranged, a part or all of the surface other than the lens unit is roughened.
The prism sheet according to any one of claims 1 to 4. The roughening is performed by regularly arranging concave shapes or convex shapes, or by regularly arranging aggregates in which concave shapes or convex shapes are randomly arranged. ,
The prism sheet according to claim 5. A primary light source;
A light guide plate having a light incident surface on which light emitted from the primary light source is incident and a light emission surface that emits incident light; and
The prism sheet according to any one of claims 1 to 6, wherein the prism sheet is disposed so as to face the light emitting surface of the light guide plate.
A surface light source device. The light incident surface is a side end surface of the light guide plate, and the light guide plate has a light incident portion having a thickness larger than other portions of the light guide plate over a predetermined length from the light incident surface,
The prism sheet is disposed at a position away from the light incident surface than the light incident portion.
The surface light source device according to claim 7. The light incident portion is formed such that the thickness gradually decreases in a direction away from the light incident surface.
The surface light source device according to claim 7 or 8.

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