JP2006323183A - Thin surface light source element, method for manufacturing the same, and liquid crystal display apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin surface light source element and a method for manufacturing the element, and to provide a liquid crystal display apparatus that uses the element. <P>SOLUTION: The surface light source element comprises at least one light-exiting means, a light guide body, and at least one light source to allow light to enter the side face of the light guide body, wherein the light-exiting means and the light guide body are formed integrated to a thickness of 0.5 mm or smaller. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thin surface light source element used in a mobile phone, a PDA, a video camera, a car navigation system, a personal computer, a computer monitor, a television receiver, an advertising billboard, etc., a manufacturing method thereof, and a liquid crystal using the same. The present invention relates to a display device.

  Liquid crystal displays that have come to be widely used as medium and large display devices such as small display devices such as mobile phones, PDAs, video cameras, car navigation systems, personal computers, computer monitors, television receivers, advertising billboards, It consists of a surface light source element (backlight) that emits light in a planar shape and a transmissive or transflective liquid crystal display panel that provides image information, and the light transmittance is controlled by the image information provided by the liquid crystal display panel. Characters and images are displayed.

  As a conventional technique related to a surface light source element, there is a method using scattered reflection to emit light from a light guide. However, since the angular distribution of emitted light is too wide, only a low luminance is obtained in the front direction. No (see Patent Document 1). For this reason, in order to increase the luminance, it is necessary to use a condensing member that controls the emission angle represented by a prism sheet in which a large number of linear prisms are arranged. However, when these components are used, there are problems such as an increase in cost and an increase in the thickness of the surface light source element.

  On the other hand, several methods for producing a surface light source element by reducing the thickness of the light guide have been proposed. Patent Document 2 exemplifies a surface light source element composed of a light guide, a reflection layer, and a light control layer, and the thickness of the light guide is 0.05 mm to 0.9 mm. According to the present invention, it is possible to reduce the thickness of the surface light source element, but since the principle of light emitted from the surface light source element is not clarified at all, the possibility of realization seems to be poor. .

  In Patent Document 3, the metal frame used for securing the rigidity of the surface light source element is omitted, and the surface light source element is sandwiched between resin films to provide rigidity, thereby achieving a reduction in thickness. However, as in Patent Document 2, the light emission principle from the surface light source element is unclear.

  Furthermore, in Patent Document 4, a diffusion pattern composed of a minute uneven pattern, a diffuse reflection ink printing pattern, or the like is provided on the back surface of a thin and flexible light guide, and a regular reflection sheet is further attached. According to the invention, light can be emitted only at a portion where a diffusion pattern and a specular reflection sheet are provided, and a flexible surface light source can be obtained by using a sheet of polycarbonate, polyvinyl chloride, polyethylene terephthalate, polypropylene or the like as a light guide. An element can be obtained. Although the light emission of the surface light source element can be confirmed by this method, since the emitted light has no directivity, there is a problem that the brightness of the emitted light in the front direction is low. In addition, it is conceivable to use a prism sheet or the like in order to impart directivity, but this is not preferable because the number of members increases and the thickness also increases.

JP 2001-43716 A JP-A-6-186558 JP 2003-242821 A JP 2000-258633 A US Pat. No. 5,396,350 JP 2005-38749 A JP 2005-38750 A JP 2004-273238 A JP 2004-268383 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a thin surface light source element characterized by being thinner and more flexible than the prior art and a method for manufacturing the same. Furthermore, it aims at providing the liquid crystal display device using this thin surface light source element.

  A thin surface light source element that solves the above problems is a surface light source comprising at least one light emitting means, a light guide, and at least one light source for making light incident on a side surface of the light guide. In the element, the light emitting means and the light guide in the surface light source element are integrally formed and have a thickness of 0.5 mm or less, and the light emitting means has a top portion in the same plane and has a light reflecting function. An output light control plate having a thickness of 0.25 mm or less formed with a plurality of convex portions having a thickness, and a light guide body having a uniform in-plane thickness and the output light control plate are bonded via the top portion of the convex portions. It is characterized by becoming.

  The method for producing a thin surface light source element of the present invention is such that after applying an adhesive to a transparent light guide film at a visible light wavelength, a long film in which the emission light control plate is disposed is bonded. Thus, a plurality of thin surface light source elements are continuously manufactured.

  Moreover, the manufacturing method of the thin surface light source element of this invention WHEREIN: The energy beam which has the energy of 4 eV or more for the elongate film in which the film for light guides transparent at visible light wavelength and / or the said emitted light control board are arrange | positioned are provided. After the surface treatment by irradiation, a plurality of thin surface light source elements are continuously produced by laminating the light guide film and the long film.

  Furthermore, the manufacturing method of the thin surface light source element of this invention is characterized by obtaining a thin surface light source element by cut | disconnecting the film in which the several surface light source element was formed in a predetermined position.

  The liquid crystal display device of the present invention uses the thin surface light source element.

  ADVANTAGE OF THE INVENTION According to this invention, the thin surface light source element characterized by being thin compared with the past and being flexible, and its manufacturing method can be provided. In addition, by using the thin surface light source element of the present invention, it is possible to provide a liquid crystal display device that is optimal for mobile use, taking advantage of the thin and lightweight features.

  The thin surface light source element of the present invention has a light emitting means and a light guide integrally formed, and has a thickness of 0.5 mm or less. If the thickness of the light emitting means and the light guide is 0.5 mm or less, a flexible thin surface light source element can be realized. The thin surface light source element is not particularly limited as long as it is a method using at least a light guide, but a dot printing method of a paint in which a diffusing material is added to the back surface of the light guide, irregularities on the surface and / or the back surface of the light guide. In a thin surface light source element having a light emitting means such as a pattern forming method for forming grooves, a scattering light guide method in which a diffusing material is added to the light guide, an optical sheet such as a reflection sheet, a diffusion sheet, or a prism sheet is provided One or more sheets must be used, and integration with a thin surface light source element is difficult. Therefore, in order to realize the present invention, a thin surface light source element in which a light guide and an outgoing light control plate having a plurality of convex portions are bonded via the tops of the convex portions of the outgoing light control plate is provided. It is necessary to use it.

  A schematic configuration diagram of the thin surface light source element 10 is shown in FIG. 1 (see Patent Documents 5, 6, and 7), and the light emission principle will be briefly described below. Light incident on the light guide 11 from the light source 12 propagates while totally reflecting inside the light guide 11. When propagating light reaches the adhesive portion 15 between the light guide 11 and the top of the convex portion 13, if the difference in refractive index between the convex portion 13 and the light guide 11 is small, the emitted light control from the adhesive portion 15 is performed. Light is extracted to the plate 14 side. Since the surface light source element 10 is based on a light emission principle that uses only total reflection without using scattered reflection, the surface light source element 10 has a feature of high light use efficiency.

  In addition, in the conventional surface light source element, it is necessary to use a condensing member for controlling the emission angle represented by a prism sheet having a large number of linear prisms. It was. On the other hand, the thin surface light source element 10 of the present invention can control the emission angle by the shape of the convex portion 13. That is, since the light extracted by the bonding portion 15 is inclined from the normal direction of the thin surface light source element, it is incident on the inclined surface of the convex portion 13 and is totally reflected or refracted. Here, on the slope, there is an interface between air and a resin material that forms a convex portion described later, and has a relatively large refractive index difference. Therefore, the light incident on the inclined surface satisfies the total reflection condition, and the light is reflected in the normal direction of the thin surface light source element and emitted to the observer side. At this time, since the directivity of the emitted light can be controlled by optimizing the inclination of the inclined surface, it is also a feature of the thin surface light source element of the present invention that a condensing member such as a prism sheet is unnecessary.

  In FIG. 1, a shape like a one-dimensional cylindrical lens is shown as the convex portion 13, but it may be a shape like a two-dimensional microlens (fly eye lens), and the shape of the convex portion is It is not limited to the above, and any shape may be used. Further, the size of the convex portion is not particularly limited, but in order to make the convex portion invisible, it is preferably 100 μm or less, and more preferably 50 μm or less.

  There is no particular limitation on the arrangement of the convex portions on the outgoing light control plate, but when placing importance on the uniformity of the thin surface light source element, the area close to the light source is sparse and the area far from the light source is densely arranged, and the arrangement density is smooth. Preferably, the modulation is performed. In this way, uniform light emission in the surface of the thin surface light source element can be realized.

  Next, the outgoing light control plate used in the present invention will be described. The main surface (hereinafter referred to as the main surface on the incident side) on which the convex portion is formed in the outgoing light control plate (hereinafter may be referred to as the main surface on the incident side) may be referred to as the main surface (hereinafter referred to as the main surface on the output side). ) May be flat or fine irregularities may be formed. When the main surface on the emission side is flat, the angular distribution of the emitted light of the thin surface light source element depends on the shape of the convex portion formed on the main surface on the incident side. On the other hand, when fine irregularities are formed on the main surface on the emission side, the angular distribution of the emitted light of the thin surface light source element is formed on the convex shape formed on the main surface on the incident side and the main surface on the emission side. Depends on fine irregularities. In other words, directivity is imparted to the outgoing light by controlling the shape of the convex portion formed on the main surface on the incident side, and the outgoing light is controlled by controlling the shape of the fine irregularities formed on the main surface on the outgoing side. It is possible to provide a desired viewing angle. “Direction of emitted light” means that the peak luminance of the emitted light from the surface light source element is inclined from the normal direction of the surface light source element (including the 0 degree inclination). The “viewing angle of” represents the half-value width with respect to the peak luminance of the light emitted from the surface light source element.

  The thickness of the outgoing light control plate in the thin surface light source element of the present invention needs to be 0.25 mm or less. Here, the thickness of the outgoing light control plate is defined by the thickness of the main surface on the incident side and the main surface on the outgoing side, and corresponds to the length from the top of the convex portion on the main surface on the incident side to the main surface on the outgoing side. To do. However, when fine irregularities are formed on the main surface on the emission side, the length is from the top of the convex portion on the main surface on the incident side to the average height of the fine irregularities on the main surface on the emission side.

  Examples of the method for producing the outgoing light control plate include a hot press molding method, an injection molding method, an extrusion molding method, and a photopolymerization molding method. However, since the outgoing light control plate cannot be continuously formed by the hot press molding method or the injection molding method, it is not preferable for use in the present invention. The extrusion method using the thermoplastic resin or the active energy ray curable resin is not preferable. A photopolymerization molding method using is suitable. In the extrusion molding method, a roll-shaped mold having a convex negative shape formed on the outgoing light control plate is used. After the thermoplastic resin is extruded into a sheet shape, the thermoplastic resin is cooled while being in contact with the mold. By doing so, a long film-like outgoing light control plate can be obtained. On the other hand, in the photopolymerization molding method, a low-viscosity active energy ray-curable resin is applied on a transparent support, and then the above-mentioned roll mold is brought into close contact with the active energy ray-curable resin layer. By irradiating active energy rays from above the transparent support in that state, a long film-like outgoing light control plate (hereinafter sometimes simply referred to as a long film) can be obtained. However, the manufacturing method of the outgoing light control plate is not limited to these methods, and any method can be used as long as the outgoing light control plate can be continuously formed. Further, since the long film-like outgoing light control plate has a thickness of 0.25 mm or less as described above, it can be wound into a roll.

  When forming fine irregularities on the main surface on the emission side of the emission light control plate, surface treatment such as sandblasting may be applied, or fine irregularities may be formed during extrusion molding or photopolymerization molding. In the case of extrusion molding, using a roll-shaped mold in which a negative shape of fine irregularities is formed and a roll-shaped mold in which a convex negative shape is formed on the outgoing light control plate, while sandwiching a thermoplastic resin By cooling, an outgoing light control plate in the form of a long film having fine irregularities formed on the main surface on the outgoing side can be obtained. In the case of photopolymerization molding, an active energy ray-curable resin is applied to the main surface on the emission side on the long film-like output light control plate having a convex shape formed on the main surface on the incident side, and then described above. A roll-shaped mold having a fine irregular negative shape formed in close contact with the active energy ray-curable resin layer and irradiated with active energy rays, thereby forming a length with fine irregularities formed on the main surface on the emission side. A long film-like outgoing light control plate can be obtained.

  Next, the manufacturing method of the thin surface light source element of this invention is demonstrated. As a light guide for a general surface light source element, a material transparent at a visible light wavelength is used. Representative examples include polymethyl methacrylate, polycarbonate, polystyrene, cyclic olefin polymer, and the like, and polymer blends and copolymer polymers of the materials listed here can also be used. However, materials other than those described above can be used as long as they are transparent at the visible light wavelength. A light guide film obtained by smoothly molding these transparent materials on both the front and back surfaces is used for the thin surface light source element of the present invention. The light guide film needs to have a uniform in-plane thickness, and preferably has a thickness of 0.25 mm or less. If the thickness is non-uniform or the surface is not smooth, the light will leak out of the light guide when propagating through the light guide while being totally reflected. The light utilization efficiency of the device is reduced. In addition, when the thickness is greater than 0.25 mm, it is difficult to wind up the light guide film, which may make it difficult to realize the method for manufacturing a thin surface light source element of the present invention.

  FIG. 2 shows a simplified process diagram for manufacturing a thin surface light source element. The above-described roll-shaped light guide film 21 is set on the unwinding portion 22 and the light guide film 21 is conveyed. A predetermined amount of the adhesive / adhesive 23 is applied to only one main surface of the light guide film 21 using an application device 24 (herein, the adhesive / adhesive means an adhesive and an adhesive). Represents a generic name). Moreover, the roll-shaped long film 25 in which the above-mentioned emission light control plate is disposed is set in the unwinding portion 26, the main surface on the incident side of the emission light control plate is used as a bonding surface, and the conveyance speed is The long film 25 is conveyed so as to be the same as the light guide film 21. The film 21 for light guide and the long film 25 are bonded together by a laminate roll 27 so that they are integrated to obtain a film 28 in which a plurality of thin surface light source elements are formed. Since the film has a total thickness of 0.5 mm or less and is flexible, the film can be wound in a roll shape by the winding portion 29.

  Although not shown in FIG. 2, when a UV curable adhesive is used as an adhesive / adhesive, the light guide film 21 and the long film 25 are bonded to each other by irradiating a predetermined amount of UV. It is also possible to do. In FIG. 2, the process of applying the adhesive / adhesive 23 to the light guide film 21 and the process of bonding the light guide film 21 and the long film 25 are shown in one. After applying the adhesive / adhesive 23 to the body film 21, the cover film that has been subjected to the release treatment is bonded and wound, and the cover film is peeled off from the light guide film 21 in the next step. And it is also possible to divide | segment into two processes of bonding the elongate film 25. FIG.

  Another method for producing the thin surface light source element of the present invention will be described with reference to FIG. The roll-shaped light guide film 21 is set on the unwinding portion 22 and the light guide film 21 is conveyed. Further, a roll-shaped long film 25 provided with an outgoing light control plate is set on the unwinding portion 26, the main surface on the incident side of the outgoing light control plate is used as a bonding surface, and the conveyance speed is the guide speed. The long film 25 is conveyed so as to be the same as the light body film 21. Next, the surface treatment device 31 performs surface treatment on the bonding surface of the light guide film 21 and / or the long film 25. Further, the light guide film 21 and the long film 25 are bonded together by a laminating roll 27 so that they are integrated to obtain a film 28 in which a plurality of thin surface light source elements are formed. Since the film has a total thickness of 0.5 mm or less and is flexible, the film can be wound up in a roll shape by the winding unit 28. Moreover, according to the bonding method by the surface treatment of this invention, since it is not necessary to use an adhesive agent, the surface light source element can be made still thinner. In addition, about the surface treatment method of the film 21 for light guides and / or the elongate film 25, the method demonstrated by patent document 8, 9 can be utilized.

  The surface treatment of the light guide film and / or the long film can be performed as follows. Examples of the surface treatment method include ultraviolet irradiation, corona discharge treatment, electron beam irradiation, ion beam irradiation and the like. The energy for the surface treatment needs to be 4 eV or more, preferably 7 eV or more. When the surface treatment energy is 4 eV or more, molecular bonds such as C—C bonds and C—H bonds can be easily broken. That is, when the energy of the energy beam to be irradiated is less than 4 eV, molecular bonds such as C—C bond and C—H bond are not broken, and sufficient tackiness / adhesiveness is not exhibited.

Examples of energy rays used for the surface treatment in the method for producing a thin surface light source element of the present invention include ultraviolet rays, corona discharge, electron beams, ion rays, and the like. Excimer lasers, Ar ⁺ lasers, Kr ⁺ lasers are particularly preferable as ultraviolet rays. , N ₂ laser, D ₂ lamp, high pressure mercury lamp, low pressure mercury lamp, Xe lamp, Hg-Xe lamp, halogen lamp, excimer lamp, or arc discharge in air, nitrogen or other gas atmosphere, corona discharge or silent discharge The thing which uses an ultraviolet lamp etc. as a generation source is mentioned. Among them, D ₂ lamp, a high pressure mercury lamp, low pressure mercury lamp, Xe lamp, Hg-Xe lamp, a halogen lamp, energy to the energy ray an ultraviolet lamp such as an excimer lamp, strength, preferred in view of the balance of the irradiation range .

  The thin surface light source element of the present invention can be obtained by cutting only the surface light source element portion of the roll-shaped film formed with the plurality of surface light source elements as described above. Examples of cutting methods include mechanical cutting with scissors and a cutter knife, thermal cutting with a carbon dioxide laser, and punching with a Thomson blade, but are not limited to these, and a plurality of surface light source elements were formed. It suffices if only a desired surface light source element portion can be cut from the film.

  Since the surface light source element of the conventional configuration had to be manufactured in a single wafer because a plate-shaped light guide was used, the manufacturing cost could not be significantly reduced, but according to the manufacturing method of the present invention, Since the thin surface light source element can be manufactured continuously, the cost can be reduced.

  By arranging a light source on the end face of the obtained thin surface light source element, light can be extracted to the viewer side. Examples of the light source used for the thin surface light source element include a linear light source such as a cold cathode tube and a point light source such as a light emitting diode (LED). Since the thin surface light source element of the present invention has a thickness of 0.5 mm or less, the light emitted from the light source can be effectively obtained only by arranging the light source having a thickness of 0.5 mm or more on the end surface of the thin surface light source element. It cannot be used. Therefore, a light guide can be used between the thin surface light source element and the light source. By using the light guide, light can be efficiently incident on a surface light source element thinner than the light emitting portion of the light source. The light incident from the light source as described above is extracted toward the observer from the exit surface side of the thin surface light source element.

  The liquid crystal display device using the thin surface light source element of the present invention is characterized by being much thinner than the conventional product, and is particularly suitable for mobile applications that require a reduction in thickness and weight. Further, by using in combination with a liquid crystal display panel using a plastic substrate, it is possible to realize not only a thin and lightweight liquid crystal display device but also a flexible liquid crystal display device.

It is a schematic block diagram which shows an example of a thin surface light source element. It is a simplified process drawing explaining the manufacturing method of the thin surface light source element of this invention. It is a simplified process diagram explaining another manufacturing method of the thin surface light source element of this invention.

Explanation of symbols

10: Thin surface light source element 11: Light guide 12: Light source 13: Convex part 14: Emission light control plate 15: Adhesive part 21: Light guide film 22: Unwinding part 23 for light guide film Adhesive 24: coating device 25: long film 26 provided with an outgoing light control plate: long film unwinding section 27: laminating roll 28: film 29 on which a plurality of thin surface light source elements are formed: thin surface Film winding unit 31 in which a plurality of light source elements are formed: surface treatment apparatus

Claims (5)

A surface light source element comprising a light guide, at least one light source for making light incident on a side surface of the light guide, and at least one light emitting means for taking out emitted light from the light guide The light emitting means and the light guide are integrally formed and have a thickness of 0.5 mm or less, and the light emitting means has a plurality of light reflecting functions with the tops being in the same plane. A light guide plate having a thickness of 0.25 mm or less in which a convex portion is formed, and a light guide body having a uniform in-plane thickness and the outgoing light control plate are bonded via the top of the convex portion. A thin surface light source element. 2. The method of manufacturing a thin surface light source element according to claim 1, wherein the emission light control plate is disposed after an adhesive is applied to a transparent light guide film in a visible light wavelength region. The manufacturing method of the thin surface light source element characterized by manufacturing a several thin surface light source element continuously by bonding a long film. The method of manufacturing a thin surface light source element according to claim 1, wherein a long film in which the film for a light guide and / or the emission light control plate transparent in the wavelength region of visible light is disposed is 4 eV or more. A thin surface characterized in that a plurality of thin surface light source elements are continuously produced by bonding the light guide film and the long film after surface treatment by irradiation with energy rays having energy Manufacturing method of light source element. 4. The method of manufacturing a thin surface light source element according to claim 2, wherein the film on which the plurality of surface light source elements are formed is cut at a predetermined position. A thin-film surface light source element according to claim 1 is used.

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