JP2012212612A - Light guide member and backlight device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a light guide member having a high light-emitting efficiency and small variations in illuminance.SOLUTION: The light guide member 100 is provided with a light guide plate 300 having opposed two principal surfaces 310, 320 and opposed two light introduction surfaces 330, 350, an adhesion part 400 formed on the principal surface 310 of the light guide plate 300, and an optical film 500 adhered to the principal surface 310 with the adhesion part 400. A thickness T of the light guide plate, a distance L between the opposed two light introduction surfaces 330, 350 and a sum S of occupying ratios of the adhesion parts 400 per unit area of the two principal surfaces 310, 320, in a portion wherein a distance to the nearer light introduction surface out of the opposed two light introduction surfaces 330, 350 in the principal surface 310 is A, is to satisfy the expression in a portion where A/L of the principal surfaces 310, 320 is 20% to 50%.

Description

  The present invention relates to a light guide member and a backlight device including the same.

  As a backlight device used in a liquid crystal display device, a sidelight type in which light from a light source is introduced from a light introduction surface which is a side surface of a light guide plate and emitted from a main surface (front surface or back surface) of the light guide plate A backlight device is known. The sidelight type backlight device has an advantage that it can be formed thinner than a direct type backlight device. In such a sidelight type backlight device, adoption of a thinner light guide plate is being studied in order to meet the demand for further thinning of the device. For example, Patent Documents 1 and 2 discuss the thin light guide plate.

JP 2005-228612 A JP 2006-210108 A

  Usually, in a backlight device, the light guide plate is not used alone, but is used in combination with an optical film such as a diffusion film, a prism film, a brightness enhancement film, a reflection sheet, or a polarizing film. Therefore, when manufacturing a backlight device, the light guide plate and the optical film are usually bonded together. The member obtained by bonding the light guide plate and the optical film in this manner is hereinafter appropriately referred to as “light guide member”. However, when the light guide plate and the optical film are used in combination, the manufacturing process of the backlight device increases, so that it is desired to develop a backlight device that can be efficiently manufactured with a small number of processes.

  In addition, a light output portion (sometimes referred to as a light extraction structure) may be formed on the main surface of the light guide plate from the viewpoint of improving the light output efficiency. Usually, the light output portion is formed as a portion protruding from the main surface of the light guide plate by a material capable of transmitting light. Usually, in such a light guide plate, the light guided in the light guide plate does not go out of the light guide plate from the portion where the light output portion of the main surface is not formed. From the portion where the portion is formed, the light exiting portion is transmitted to the outside of the light guide plate.

  In general, a light guide plate for a backlight device is required to have high light output efficiency and small variation in illuminance. However, in the case of a thin light guide plate, the number of internal reflections of light introduced from the side surface tends to be significantly larger than that of a thick light guide plate. For this reason, when the light output part is formed on a thin light guide plate having the same arrangement and size as a conventional thick light guide plate, the variation in illuminance increases and uneven illuminance may occur. Specifically, as the number of internal reflections of light increases, the illuminance increases because light easily exits from the part near the light source on the main surface, and is guided at the part far from the light source on the main surface. There was a tendency for the amount of light emitted to decrease and the illuminance to decrease. Under such circumstances, it has been difficult to improve both the light output efficiency and the variation in illuminance in a balanced manner in a backlight device including a thin light guide plate.

  The present invention was devised in view of the above-described problems, and has a high light output efficiency and a small variation in illuminance, and a backlight device that includes the light guide member and can be manufactured with fewer steps than in the past. The purpose is to provide.

As a result of intensive studies to solve the above-mentioned problems, the inventor uses a bonding portion that bonds the light guide plate and the optical film as the light output portion, and a step of forming the light output portion and a step of bonding the light guide plate and the optical film. Therefore, it has been found that the number of steps can be reduced in the method of manufacturing the light guide member and the backlight device. Moreover, in such a light guide member, if the occupation ratio of the adhesive portion in a predetermined portion of the main surface of the light guide plate is within an appropriate range according to the position of the point, both light emission efficiency and illuminance variation are improved. Found that you can. Furthermore, it has been found that the appropriate range of the occupation ratio is expressed by a function of the thickness of the light guide plate, the distance between the light introduction surfaces, and the distance from the point in question to the light introduction surface. Based on the above findings, the present inventor has completed the present invention.
That is, the gist of the present invention is the following [1] to [3].

[1] A light guide plate having two opposite main surfaces and two opposite light introduction surfaces, an adhesive portion formed on at least one of the main surfaces of the light guide plate, and the adhesive portion of the light guide plate are formed A light guide member comprising an optical film adhered to the principal surface by the adhesive portion,
The thickness of the light guide plate is T (mm), the distance between the two light introduction surfaces facing each other is L (mm), and the light of the two light introduction surfaces facing each other on the main surface is the closest When the total occupancy ratio of the bonded portion per unit area of the two main surfaces facing each other at a portion where the distance to the introduction surface is A (mm) is S (%), the A / A light guide member satisfying the following formula I in a portion where L is 20% to 50%.
[2] The light guide member according to [1], wherein A / L of the main surface of the light guide plate satisfies any of the following formulas II to IV in a portion where the A / L is 20% to 50%.
[3] A backlight device comprising the light guide member according to [1] or [2].

  The light guide member and the backlight device of the present invention have high light output efficiency and small variations in illuminance. Moreover, the light guide member and the backlight device of the present invention can be manufactured with a smaller number of processes than in the past.

FIG. 1 is a perspective view schematically showing an outline of a backlight device as a first embodiment of the present invention. FIG. 2 is a diagram schematically illustrating the backlight device according to the first embodiment of the present invention, and is a diagram illustrating a state in which the light guide plate is cut along a plane perpendicular to the main surface. FIG. 3 is a perspective view schematically showing the light guide plate according to the first embodiment of the present invention. FIG. 4 is a graph for explaining the formula I. FIG. 5 is a graph for explaining the formulas II to IV. FIG. 6 is a perspective view schematically showing an example of the shape of the bonding portion. FIG. 7 is a perspective view schematically showing an example of the shape of the bonding portion. FIG. 8 is a diagram schematically illustrating a backlight device as a second embodiment of the present invention, and is a diagram illustrating a state in which the light guide plate is cut along a plane perpendicular to the main surface. FIG. 9 is a diagram schematically showing a backlight device as a third embodiment of the present invention, and is a diagram showing a state in which the light guide plate is cut along a plane perpendicular to the main surface. FIG. 10 is a diagram schematically illustrating an example of a method for manufacturing the light guide member. FIG. 11 is a diagram for explaining simulation conditions set in the simulation performed in the first embodiment. FIG. 12 shows the total of the distance A from one light introduction surface in Example 1, the distance L between the light introduction surfaces facing each other, the thickness T of the light guide plate, and the occupation ratio of the adhesive portion on the main surface of the light guide plate. It is a figure which shows the relationship of S about the part whose distance A is 0 mm, 100 mm, 200 mm, 300 mm, 400 mm, and 500 mm. FIG. 13 shows the total of the distance A from one light introduction surface in Example 2, the distance L between the light introduction surfaces facing each other, the thickness T of the light guide plate, and the occupation ratio of the adhesive portion on the main surface of the light guide plate. It is a figure which shows the relationship of S about the part whose distance A is 0 mm, 100 mm, 200 mm, 300 mm, 400 mm, and 500 mm. FIG. 14 shows the total of the distance A from one light introduction surface in Example 3, the distance L between the light introduction surfaces facing each other, the thickness T of the light guide plate, and the occupation ratio of the adhesive portion on the main surface of the light guide plate. It is a figure which shows the relationship of S about the part whose distance A is 0 mm, 100 mm, 200 mm, and 300 mm. FIG. 15 shows the total of the distance A from one light introduction surface in Example 4, the distance L between the light introduction surfaces facing each other, the thickness T of the light guide plate, and the occupation ratio of the adhesive portion on the main surface of the light guide plate. It is a figure which shows the relationship of S about the part whose distance A is 0 mm, 100 mm, 200 mm, and 300 mm. FIG. 16 shows the total of the distance A from one light introduction surface in Comparative Example 1, the distance L between the light introduction surfaces facing each other, the thickness T of the light guide plate, and the occupation ratio of the adhesive portion on the main surface of the light guide plate. It is a figure which shows the relationship of S about the part whose distance A is 0 mm, 100 mm, 200 mm, 300 mm, 400 mm, and 500 mm. FIG. 17 shows the total of the distance A from one light introduction surface in Comparative Example 2, the distance L between the light introduction surfaces facing each other, the thickness T of the light guide plate, and the occupation ratio of the adhesive portion on the main surface of the light guide plate. It is a figure which shows the relationship of S about the part whose distance A is 0 mm, 100 mm, 200 mm, 300 mm, 400 mm, and 500 mm. FIG. 18 shows the total of the distance A from one light introduction surface in Comparative Example 3, the distance L between the light introduction surfaces facing each other, the thickness T of the light guide plate, and the occupation ratio of the adhesive portion on the main surface of the light guide plate. It is a figure which shows the relationship of S about the part whose distance A is 0 mm, 100 mm, and 200 mm.

Hereinafter, the present invention will be described in detail with reference to embodiments and examples, but the present invention is not limited to the following embodiments and examples, and departs from the gist of the present invention and its equivalent scope. Any change can be made without departing from the scope.
In the following description, the directions of the components are “parallel” and “orthogonal” unless otherwise specified, including errors within a range that does not impair the effects of the present invention, for example, within ± 5 °. May be. Further, “along” in a certain direction means “in parallel” in a certain direction.

[First embodiment]
FIG. 1 is a perspective view schematically showing an outline of a backlight device as a first embodiment of the present invention. FIG. 2 is a diagram schematically showing the backlight device as the first embodiment of the present invention, and is a diagram showing a state in which the light guide plate is cut along a plane perpendicular to the main surface.

  As shown in FIG. 1, the backlight device 10 as the first embodiment of the present invention includes a light guide member 100 and light sources 210 and 220.

  The light guide member 100 includes a light guide plate 300, an adhesive portion 400, and an optical film 500. Here, the light guide plate 300 includes not only a rigid member but also a flexible member such as a resin film. In the present embodiment, the light guide plate 300 is a rectangular parallelepiped member, and has two main surfaces 310 and 320 facing each other and four side surfaces 330 to 360. Of the side surfaces 330 to 360, the two opposite side surfaces 330 and 350 are light introduction surfaces, and the light source 210 is installed at a position where the side surface 330 can be irradiated with light, and the side surface 350 can be irradiated with light. A light source 220 is installed. Therefore, as shown in FIG. 2, the light B emitted from the light sources 210 and 220 is introduced into the light guide plate 300 through the side surfaces 330 and 350 that are light introduction surfaces, and internally reflected by the main surfaces 310 and 320. The light guide plate 300 is guided repeatedly.

  Since the side surface 330 and the side surface 350 function as a light introduction surface, they are referred to as “light introduction surface 330” and “light introduction surface 350”, respectively, in the following description. Of the two main surfaces of the light guide plate 300, one main surface 310 is appropriately referred to as “front surface 310”, and the other main surface 320 is referred to as “back surface 320”.

  The front surface 310 and the back surface 320 of the light guide plate 300 are at least in the axial direction of the light sources 210 and 220 (that is, the direction of the chief rays of the emitted light, hereinafter may be abbreviated as “optical axis direction”). Usually, it is a flat surface without irregularities and undulations. In the present embodiment, the optical axis direction is a direction orthogonal to the light introduction surfaces 330 and 350. In addition, the flat surface here refers to a surface having an arithmetic average roughness Ra of 0.05 μm or less, preferably 0.02 μm or less, more preferably 0.01 μm or less, when measured in the optical axis direction. Thus, since the arithmetic average roughness Ra in the optical axis direction is small, it is possible to suppress the emission of light from the portion 370 where the bonding portion 400 is not formed. Therefore, it is possible to prevent light from being unintentionally taken out from the portion 370 where the adhesive portion 400 is not formed, and to more reliably suppress illuminance unevenness. Moreover, although there is no restriction | limiting in a lower limit, it is 0.001 micrometer or more normally in an optical axis direction. The arithmetic average roughness Ra employs a value measured in the optical axis direction by a method defined in JIS B601-2001. Further, since the front surface 310 and the back surface 320 are parallel to each other in macro, the thickness T (see FIG. 3) of the light guide plate 300 is uniform in the in-plane direction of the front surface 310 and the back surface 320. It has become.

  If the smoothness in the optical axis direction is satisfied, the direction orthogonal to the optical axis direction is limited to the shape of the front surface 310 and the back surface 320 unless the light guide in the light guide plate 300 is disturbed. There is no. For example, the front surface 310 and the back surface 320 may be flat in a direction orthogonal to the optical axis direction.

  For example, the front surface 310 and the back surface 320 may be provided with bowl-shaped irregularities extending parallel to the optical axis direction. As a result, a groove parallel to the optical axis direction is formed on the front surface 310 and the back surface 320, so that the light traveling in the light guide plate 300 is reflected in the optical axis direction by internal reflection at the slope of the groove. It is possible to prevent diffusion in the orthogonal direction. The unevenness may be formed only on part of the front surface 310 and the back surface 320, or may be formed on all of the front surface 310 and the back surface 320. Examples of the shape of a cross section obtained by cutting the unevenness by a plane orthogonal to the extending direction include a polygonal shape such as a triangular shape, and a partial shape of a circle such as a semicircular shape and a semielliptical shape. These shapes are, for example, so-called prism shapes when the cross section is a polygonal shape, and so-called lenticular shapes when the cross section is a partial shape of a circle. These shapes may be arbitrarily combined and mixed, and a flat portion may be provided between each groove or ridge.

  However, the main surface (in the present embodiment, the front surface 310) on which the adhesive portion 400 is formed is more preferably smooth in the direction orthogonal to the optical axis direction in addition to the optical axis direction. When the groove is formed on the main surface on which the adhesive portion 400 is formed as described above, when forming the adhesive portion 400, the material forming the uncured adhesive portion moves along the groove due to capillary action, so that bleeding occurs. An unexpected phenomenon such as this may occur and it may be difficult to control the total S of the occupation ratio. Therefore, it is preferable from the viewpoint of facilitating the manufacture of the light guide member 100 to form irregularities only on the main surface opposite to the main surface on which the adhesive portion 400 is formed (in this embodiment, the back surface 320).

  Furthermore, although the side surfaces 340 and 360 of the light guide plate 300 are usually flat surfaces without unevenness and unevenness, an uneven structure may be provided as necessary. For example, when a plurality of light guide plates are combined and used as an integrated light guide plate, the side surfaces 340 and 360 may have a concavo-convex structure for the purpose of combining the light guide plates. If a specific example is given, you may provide the fitting part which can mutually be fitted and can fix a some light-guide plate. However, also in this case, like the front surface 310 and the back surface 320, the side surfaces 340 and 360 are preferably smooth in the optical axis direction.

  Usually, the light B (see FIG. 2) guided through the light guide plate 300 is incident on the front surface 310, the back surface 320, and the side surfaces 340 and 360 at a large incident angle. Internal reflection occurs at the front surface 310, the back surface 320, and the side surfaces 340 and 360, which are interfaces between the air layer and the air layer. By repeating such internal reflection, the light B emitted from the light sources 210 and 220 is guided in the light guide plate 300.

  The thickness T (see FIG. 3) of the light guide plate 300 is usually 0.020 mm or more, preferably 0.05 mm or more, more preferably 0.10 mm or more, and usually 2.0 mm or less, preferably 1.5 mm or less. Preferably it is 1.0 mm or less. Since the light guide plate 300 of the present embodiment can be reduced in thickness as described above, the thickness of the unit when incorporated in a lighting device or a liquid crystal display device as a unit can be reduced or reduced in weight. However, if the thickness T of the light guide plate 300 is excessively thin, it may be difficult to manufacture or the handling property may be impaired. Therefore, the thickness T has a lower limit as described above.

  As shown in FIG. 2, an adhesive portion 400 is formed on the front surface 310 of the light guide plate 300. The bonding portion 400 is a member that bonds the light guide plate 300 and the optical film 500 together. The bonding portion 400 is a part that functions as an optical path that connects the light guide plate 300 and the optical film 500.

  The adhesive portion 400 is bonded to the front surface 310 of the light guide plate 300 and the main surface 510 of the optical film 500. As a result, the light guide plate 300 and the optical film 500 are integrated by bonding by the bonding portion 400, and an interface between the light guide plate 300 and the bonding portion 400 is formed. An interface between the two is also formed between the film 500. The refractive index difference between the light guide plate 300 and the adhesive portion 400 at the portion 410 where the adhesive portion 400 of the front surface 310 is formed (that is, the interface between the light guide plate 300 and the adhesive portion 400) is usually the front surface. The difference in refractive index between the light guide plate 300 and the air layer at a portion 370 where the adhesive portion 400 is not formed (that is, the interface between the light guide plate 300 and the air layer) 370 is smaller. For this reason, even the light B having an internal angle caused by an incident angle being too large at the interface 370 between the light guide plate 300 and the air layer can be transmitted through the interface 410 between the light guide plate 300 and the bonding portion 400. The light B thus extracted from the light guide plate 300 passes through the bonding portion 400 and enters the optical film 500 through the interface 420 between the bonding portion 400 and the optical film 500. Thereafter, the light B passes through the optical film 500 and reaches the main surface 520 of the optical film 500 opposite to the light guide plate 300. In general, the main surface 520 opposite to the light guide plate 300 of most of the optical films 500 is formed of a rough surface or a surface that is not parallel to the main surface 510, unlike the main surface 510 on the light guide plate 300 side. For this reason, the light that has entered the optical film 500 exceeds the critical reflection angle at the main surface 520 and passes through the main surface 520 to exit to the outside of the optical film 500. In addition, when the optical film 500 has haze, the light entering the optical film 500 exceeds the critical reflection angle by changing the direction of the light, and is emitted from the optical film 500 as well. In this way, the light B guided in the light guide plate 300 can pass through the adhesive portion 400 and the optical film 500 and can go out of the light guide member 100.

  However, in the light guide member 10 of the present embodiment, predetermined portions of the front surface 310 and the back surface 320 which are main surfaces of the light guide plate 300 (specifically, A / L described later is 20% to 50%). The following formula I is satisfied:

FIG. 3 is a perspective view schematically showing the light guide plate according to the first embodiment of the present invention. As shown in FIG. 3, in the above formula I, T (mm) represents the thickness of the light guide plate 300.
In the above formula I, L (mm) represents the distance between the two light introduction surfaces 330 and 350 that face each other.
Further, in the above-mentioned formula I, S (no unit) is two opposing main surfaces (that is, the front surface 310 and the back surface 320) in the portion P1 of the front surface 310 or the back surface 320 that is the main surface. Represents the total occupancy ratio of the bonded portion 400 (not shown in FIG. 3) per unit area.
The portion P1 is a distance from the front light surface 310 or the back surface 320, which is the main surface, to the light light introduction surface 330 or 350 which is the closest of the two light light introduction surfaces 330 and 350 facing each other. Represents the part. That is, in the above formula I, A (mm) represents the distance from the portion P1 to the closest surface of the two light introduction surfaces 330 and 350 facing each other. Therefore, the minimum value of A is 0 mm, and the maximum value of A is 0.5L.

  Regarding the total occupancy S, the occupancy ratio of the adhesive portion 400 in the portion P1 is the main surface opposite to the main surface P1 of one main surface (the front surface 310 in the present embodiment). (In the present embodiment, it refers to the ratio of the area of the portion where the adhesive portion 400 is formed in the portion P1 to the total area of the portion P2 facing the portion P1 in the back surface 320). The area of the portion where the bonding portion 400 is formed refers to the area of the portion where the bonding portion 400 is in contact with the main surface of the light guide plate 300 (in this embodiment, the front surface 310). Say the area of the bottom. The total occupation ratio is the occupation ratio of the adhesive portion 400 in the portion P1 of one main surface (in the present embodiment, the front surface 310) and the other main surface (in the present embodiment, the back surface 320). The total of the occupying ratio of the adhesive portion in the portion P2 facing the portion P1. Furthermore, the portion P2 facing the portion P1 on the back surface 320 means a portion where the perpendicular of the front surface 310 passing through the portion P1 and the back surface 320 intersect.

  Expression I is represented by a graph as shown in FIG. As can be seen from FIG. 4, the expression I indicates that the parameter S · L / T falls within a predetermined range represented by the cubic function of the parameter A / L (that is, the hatched portion in FIG. 4). By satisfying Formula I in predetermined portions of the front surface 310 and the back surface 320 of the light guide plate 300, it is possible to achieve both an increase in light output efficiency and suppression of variations in illuminance. When S · L / T falls below the lower limit of Formula I at predetermined portions of the front surface 310 and the back surface 320 of the light guide plate 300, the light introduced into the light guide plate 300 through the light introduction surfaces 330 and 350 Most of the light cannot pass through the bonding portion 400 and is lost by being emitted to the outside through the light introduction surfaces 330 and 350 on the opposite side to the introduced portion, so that the light emission efficiency may be lowered. In addition, when S · L / T exceeds an upper limit value in predetermined portions of the front surface 310 and the back surface 320 of the light guide plate 300, light introduced from the light introduction surfaces 330 and 350 enters the light introduction surfaces 330 and 350. A large amount of light is transmitted through the bonding portion 400 at a nearby point, and the amount of light emitted from the main surface 520 of the optical film 500 increases at a point near the light introduction surfaces 330 and 350, which may increase the variation in illuminance. Further, when S · L / T falls below the lower limit of Formula I in a part of a predetermined portion of the front surface 310 of the light guide plate 300, the illuminance is locally reduced in that portion, resulting in variations in illuminance. Moreover, there is a possibility that the light emission efficiency is lowered by the amount of local decrease in illuminance. In addition, if S · L / T exceeds the upper limit value in a predetermined portion of the front surface 310 of the light guide plate 300, the illuminance may increase locally in that portion, resulting in variations in illuminance. is there.

  According to Formula I, when forming the adhesive portion 400 on the front surface 310 and the back surface 320 which are the main surfaces of the light guide plate 300, the position of the adhesive portion 400 on the front surface 310 and the back surface 320, It can be seen that if the occupancy ratio and dimensions are used, it is possible to achieve both higher light output efficiency and less variation in illuminance.

  For example, it can be seen from Formula I that the bonding portion 400 is preferably formed densely as the distance from the light introduction surfaces 330 and 350 increases. When a large amount of light passes through the adhesive portion 400 and exits to the outside at a point close to the light introduction surfaces 330 and 350, a sufficient amount of light is not guided to the point far from the light introduction surfaces 330 and 350, and the light guide member Illuminance may be insufficient near the center of 100. Furthermore, from the formula I, the occupation ratio of the adhesive portion 400 increases not in a linear manner (that is, in a linear function) according to the distance from the light introduction surfaces 330 and 350 but in a curved manner. It can also be seen that it is preferable.

  In addition, it can be seen from Formula I that, for example, the thicker the light guide plate 300 is, the more preferable the adhesive portion 400 is formed densely. If the thickness T changes, not only the appropriate setting of the position, occupation ratio, dimensions, etc. of the bonding portion 400 changes, but also how to set the bonding portion 400 specifically according to the thickness T. The formula I has technical significance in that

  Further, it can be seen from the formula I that, for example, it is preferable to adopt the total occupation ratio S instead of the occupation ratio of the adhesive portion 400 as an index indicating how dense the adhesive portion 400 is formed. . If only the occupancy ratio of the bonding portion 400 in one main surface (for example, the front surface 310) of the two main surfaces is considered, the bonding portion formed on the other main surface (for example, the back surface 320). By passing through the light and exiting the light guide member 100, the influence of the light lost from the light guide plate 300 is overlooked.

  Moreover, Formula I is arbitrary in other parts, if at least A / L consists of 20%-50% of parts. Even in the 20% portion in the vicinity of the near light introduction surfaces 330 and 350, the variation in illuminance can be reduced and the light output efficiency can be increased even if the formula I is not satisfied. However, from the viewpoint of further suppressing variation in illuminance, it is preferable that Formula I holds in all parts.

  Furthermore, in the light guide member 100 of the present embodiment, the following formulas II to IV are used when the A / L of the front surface 310 and the back surface 320 which are the main surfaces of the light guide plate 300 is 20% to 50%. Is preferably satisfied, and more preferably, any part of the following formulas II to IV is satisfied in all portions.

  In Formula II to Formula IV, parameters T, L, S, and A are all the same as in Formula I.

  Expressions II to IV are represented by graphs as shown in FIG. As can be seen from FIG. 5, the expressions II to IV represent that the parameter S · L / T falls within a predetermined range represented by the cubic function of the parameter A / L. Formulas II to IV define that the parameter S · L / T falls within a narrower range than that expressed by Formula I. By satisfying Formula II to Formula IV, it is possible to more stably suppress variation in illuminance.

  By satisfy | filling said Formula I, the light emission efficiency of the light guide member 100 can be normally 85% or more, and the standard deviation (sigma) of illumination intensity in each point of the main surface 520 of the optical film 500 of the light guide member 100 is 1%. It can be: If the light emission efficiency is thus high and the standard deviation σ of the illuminance is thus small, it can be said that the backlight device has sufficient performance. In addition, light output efficiency represents the ratio of the light which permeate | transmitted the adhesion part 400 and was emitted from the main surface 520 of the optical film 500 among the light introduce | transduced in the light-guide plate 300 from the light introduction surfaces 330 and 350. FIG. The standard deviation σ of illuminance is an index value that represents the degree of variation in illuminance. The smaller the standard deviation σ, the smaller the variation in illuminance.

  The shape of the bonding portion 400 is arbitrary as long as the effects of the present invention are not significantly impaired. Therefore, for example, as shown in FIG. 6, the bonding portion 400 may be a linear portion extending in a predetermined direction. When the bonding portion 400 is a linear portion extending in a predetermined direction, the cross-sectional shape of the bonding portion 400 (the cross-sectional shape cut by a plane perpendicular to the extending direction) is arbitrary. Furthermore, when the bonding portion 400 is a linear portion extending in a predetermined direction, the extending direction of the bonding portion 400 is also arbitrary, and the extending directions of the bonding portions 400 may be aligned, You may do it. Moreover, the adhesion part 400 may be a part formed in a dot shape as shown in FIG.

  However, when the adhesion part 400 is a linear part as shown in FIG. 6, it is preferable that the width W satisfies the following condition among the dimensions of the adhesion part 400. That is, when the thickness of the light guide plate 300 is 1 mm or less, the width W is preferably 0.5 mm or less, and more preferably 0.3 mm or less. When the thickness of the light guide plate 300 is greater than 1 mm and 3 mm or less, the width W is preferably 1.5 mm or less, and preferably 0.5 mm or less. By keeping the width W in such a range, it is possible to make it difficult to visually recognize the bonding portion 400, and thus it is possible to suppress dot appearance and partial illuminance unevenness. Here, the width W of the bonding portion 400 represents the length of the bottom of a cross section obtained by cutting the bonding portion 400 along a plane perpendicular to the extending direction, and is usually the interface between the light guide plate 300 and the bonding portion 400. Match the width. The dot appearance means that when the light guide member 100 and various optical films are assembled as the backlight device 10, the observer can visually recognize the light emitted through the adhesive portion 400 as a bright line or a bright spot. The phenomenon that becomes.

  Moreover, when the adhesion part 400 is the dotted | punctate site | part 400 which has a circular or substantially circular bottom face as shown in FIG. 7, the diameter R of the bottom face among the dimensions of the adhesion part 400 satisfies the following condition. Is preferred. That is, when the thickness of the light guide plate 300 is 1 mm or less, the diameter R is preferably 0.5 mm or less, and more preferably 0.3 mm or less. When the thickness of the light guide plate 300 is greater than 1 mm and 2 mm or less, the diameter R is preferably 1.5 mm or less, and more preferably 0.5 mm or less. By keeping the diameter R in such a range, it is possible to make it difficult to visually recognize the bonding portion 400, and thus it is possible to suppress dot appearance and partial illuminance unevenness. Here, the diameter R of the bottom surface of the bonding portion 400 usually matches the diameter of the interface between the light guide plate 300 and the bonding portion 400.

  In addition, the shape and dimension of the plurality of bonding portions 400 may be the same or different. Therefore, you may make it use combining the adhesion part 400 of 2 or more types of different shapes and dimensions.

  The parallel light transmittance of the bonding portion 400 is not particularly defined. As described above, it is not necessary for the bonding portion 400 to change the direction of the light totally reflected inside the light guide plate 300 by its own haze, and the optical film 500 may change the direction of the light and emit light. It is.

  In the present embodiment, in order to satisfy the formula I in a portion where the A / L of the front surface 310 and the back surface 320 of the light guide plate 300 is 20% to 50%, the bonding portion is formed in the in-plane direction of the front surface 310. The occupation ratio of 400 is not usually uniform and non-uniform in the in-plane direction. At this time, for example, it is preferable to divide the front surface 310 into a plurality of portions according to the distance from the light introduction surfaces 330 and 350, and to change the occupation ratio of the adhesive portion 400 in each portion into a gradation. . Moreover, it is preferable that the difference of the occupation ratio between adjacent parts among the divided parts is small. Furthermore, as the distance from the light introduction surfaces 330 and 350 increases, it is preferable that the width of the portion divided as described above (usually, the dimension in the direction orthogonal to the light introduction surfaces 330 and 350) is reduced. . This is for more stably suppressing variations in illuminance.

An optical film 500 shown in FIG. 1 is a film bonded to the front surface 310 of the light guide plate 300 by the bonding portion 400. The optical film 500 may be any film as long as it transmits at least part of the light guided through the light guide plate 300 and transmitted through the bonding portion 400. What is necessary is just to select the kind of specific optical film 500 according to the use of the backlight apparatus 10. FIG.
In the present embodiment, since light is emitted from the main surface 520 of the optical film 500 to the outside of the light guide member 100, the main surface 520 of the optical film 500 functions as a light output surface of the light guide member 100.

From the viewpoint of efficiently extracting light from the optical film 500, the main surface 520 of the optical film 500 is more preferably a rough surface having irregularities rather than a flat surface. Here, the rough surface means a surface having an arithmetic average roughness Ra larger than a flat surface.
Further, for example, a light extraction structure may be formed on the main surface 520 of the optical film 500 by printing with white ink (for example, screen printing, inkjet printing, etc.), application of diffusion beads, and various rough surface processing. .

  Although there is no restriction | limiting in particular in the thickness of the optical film 500, Usually, 0.02 mm or more, Preferably it is 0.05 mm or more, More preferably, it is 0.10 mm or more, Usually, 3.0 mm or less, Preferably it is 1.0 mm or less, More preferably Is 0.5 mm or less. In addition, when using the optical film 500 with a light transmittance, the one where the thickness is thinner is more preferable. This is because, in general, the base polymer of the optical film 500 is often colored. When the thickness is thick, the optical path length becomes long, and as a result, there is a high possibility that the wavelength component of the emitted light will change. Further, the backlight device 10 can be thinned by reducing the thickness of the optical film 500.

The light sources 210 and 220 are devices that irradiate light onto the light introduction surfaces 330 and 350 of the light guide plate 300. The light sources 210 and 220 are usually installed so that the axial direction of the light sources 210 and 220 (that is, the direction of the principal ray of emitted light; the optical axis direction) is orthogonal to the light introduction surfaces 330 and 350.
As the light sources 210 and 220, a linear light source or a point light source may be used, but a point light source is preferably used. This is because when a point light source is used, the light source can be designed to be small. Increasing the light incident efficiency can be achieved by reducing the light source.

  The light sources 210 and 220 installed opposite to each other are usually optically identical in order to simplify the optical design, use the same member, and minimize the number of manufactured parts. Optically the same means that the overall illuminance and light distribution characteristics of the light sources 210 and 220 are substantially the same, and it can be said that they are usually optically identical when the same product is used as the light sources 210 and 220. . Also in the present invention, the light sources 210 and 220 use the same optical source.

  An example of the point light source is an LED (Light Emitting Diode). LEDs are high light emission efficiency and are excellent light sources from the viewpoint of energy saving. In the present embodiment, it is assumed that LEDs are used as the light sources 210 and 220. The light sources 210 and 220 are supplied with electric power from a power source (not shown), and can emit light individually by the supplied electric power.

  The backlight device 10 as the first embodiment of the present invention is configured as described above. For this reason, in use, the light sources 210 and 220 are caused to emit light, and the light introduction surfaces 330 and 350 are irradiated with light. The light applied to the light introduction surfaces 330 and 350 is introduced into the light guide plate 300 through the light introduction surfaces 330 and 350. The introduced light is guided through the light guide plate 300 while repeating internal reflection on the front surface 310 and the back surface 320 and the side surfaces 340 and 360 which are the main surfaces. The guided light passes through the adhesive portion 400 and the optical film 500 and exits from the main surface 520 of the optical film 500 to the outside of the light guide member 100. Thereby, the backlight device 10 functions as a surface light emitting device having the main surface 520 of the optical film 500 as a light exit surface.

  Furthermore, in the backlight device 10 of the present embodiment, the A / L of the front surface 310 and the back surface 320 of the light guide plate 300 satisfies the above-described formula I at a portion of 20% to 50%. The light emission efficiency can be increased, and variations in illuminance can be suppressed. Such an effect is particularly remarkable when the light guide plate 300 having a small thickness T is used. Therefore, according to the backlight device 10 of the present embodiment, it is possible to realize all of downsizing, thinning, and weight reduction, improvement of light output efficiency, and suppression of illuminance unevenness.

  Moreover, in this embodiment, since the adhesion part 400 functions as a light emission part which takes out light from the light-guide plate 300, it is not necessary to provide the adhesion part 400 and the light emission part separately. Therefore, since the process of providing the adhesion part 400 and the process of providing the light-emitting part can be performed in one process when the light guide member 100 is manufactured, the number of processes at the time of manufacturing is reduced and the manufacturing efficiency is improved. Can do.

  Further, as compared with the case where the light guide plate and the optical film are separately prepared when the backlight device is manufactured, the light guide plate 300 and the optical film 500 are bonded together by the bonding portion 400 as in the present embodiment and guided in advance. If the optical member 100 is prepared, handling is easy and it can suppress that a foreign material mixes between the light-guide plate 300 and the optical film 500 when manufacturing the backlight apparatus 10. FIG.

  Furthermore, in the light guide member 100, the front surface 310, which is the main surface of the light guide plate 300, is covered with the optical film 500, so that the light guide plate 300 can be prevented from being damaged.

The embodiment of the present invention has been specifically described above, but the above-described embodiment may be further modified.
For example, the light guide plate 300 may have a shape other than a rectangular parallelepiped as shown in FIG.
Further, for example, lens-like planar structures may be provided on the light introduction surfaces 330 and 350 of the light guide member 100 for various purposes. By imparting an appropriate shape as the planar structure, the light incident efficiency to the light guide plate 300 is improved, or when the light sources 210 and 220 are point light sources, the point light sources and the point light sources installed apart from each other are provided. It is also possible to level the part between the light sources where the amount of light guided is relatively small.
Further, for example, a reflection sheet that reflects light may be used as the optical film 500. When the optical film 500 is a film that does not have optical transparency such as a reflection sheet, the light that has entered the bonding portion 400 is reflected at the interface 420 between the bonding portion 400 and the optical film 500, and the light guide plate 100 and the bonding member It emits light from 400. In particular, when the optical film 500 is a reflective sheet, most of the light exits through the back surface 320 of the light guide plate 300 (see the third embodiment).

[Second Embodiment]
FIG. 8 is a diagram schematically illustrating a backlight device as a second embodiment of the present invention, and is a diagram illustrating a state in which the light guide plate is cut along a plane perpendicular to the main surface.

  As shown in FIG. 8, in the backlight device 20 as the second embodiment of the present invention, an adhesive portion 600 is formed on the back surface 320 of the light guide plate 300, and the optical film is formed on the back surface 320 of the light guide plate 300 by the adhesive portion 600. By adhering 700, the adhesive portions 400, 600 and the optical films 500, 700 are formed on both the front surface 310 and the back surface 320, which are the two main surfaces of the light guide plate 300, This is the same as the backlight device 10 according to the first embodiment. At this time, the bonding portion 400 of the front surface 310 and the bonding portion 600 of the back surface 320 may be the same in shape, size, occupation ratio, or the like. The optical film 500 adhered to the front surface 310 and the optical film 700 adhered to the back surface 320 may be the same type of film or different types of films.

  Also in the backlight device 20 of the present embodiment, as in the first embodiment, the A / L of the front surface 310 and the back surface 320 which are the main surfaces of the light guide plate 300 is 20% to 50%. It is preferable that I is satisfied and any one of the formulas II to IV is satisfied. Thereby, both raising the light emission efficiency and suppressing the variation in illuminance can be realized.

  Further, according to the backlight device 20 of the present embodiment, not only the main surface 520 of the optical film 500 bonded to the front surface 310 of the light guide plate 300 but also the main surface of the optical film 700 bonded to the back surface 320. Light can also be emitted from 710. At this time, normally, the proportion occupied by the adhesive portion 400 and the adhesive portion 600 is distributed to a substantially constant ratio within a range satisfying the formula I according to the ratio of light desired to be emitted from the main surface 520 and the main surface 710. .

Moreover, according to the backlight apparatus 20 as 2nd embodiment of this invention, the same advantage as the backlight apparatus 10 which concerns on 1st embodiment can be acquired.
Furthermore, the backlight device 20 as the second embodiment of the present invention may be modified and implemented in the same manner as the first embodiment.

[Third embodiment]
FIG. 9 is a diagram schematically showing a backlight device as a third embodiment of the present invention, and is a diagram showing a state in which the light guide plate is cut along a plane perpendicular to the main surface.

  As shown in FIG. 9, in the backlight device 30 as the third embodiment of the present invention, an adhesive portion 600 is formed on the back surface 320 of the light guide plate 300, and the optical film is formed on the back surface 320 of the light guide plate 300 by the adhesive portion 600. As in the backlight device 10 according to the first embodiment, except that the diffuse reflection sheet 800 is adhered. At this time, the bonding portion 400 of the front surface 310 and the bonding portion 600 of the back surface 320 may be the same in shape, size, occupation ratio, or the like.

  The diffuse reflection sheet 800 is a film that diffusely reflects light incident on the main surface 810. Accordingly, the light B that has entered the adhesive portion 600 through the interface 610 between the adhesive portion 600 and the light guide plate 300 formed on the back surface 320 of the light guide plate 300 is diffused at the interface 620 between the adhesive portion 600 and the diffuse reflection sheet 800. The light is reflected and returns to the light guide plate 300 through the interface 610 again. Usually, the light B reflected in this way is incident on the front surface 310, which is the main surface opposite to the diffuse reflection sheet 800, at an angle different from that before reflection, so that a certain ratio is transmitted through the front surface 310. Then, the light passes through the optical film 500 and is emitted to the outside of the light guide member 100.

  In the backlight device 30 of this embodiment as well, as in the first embodiment, the A / L of the front surface 310 and the back surface 320 which are the main surfaces of the light guide plate 300 is 20% to 50%. In Formula 1, it is preferable that Formula I is satisfied, and that any one of Formulas II to IV is satisfied. Thereby, both raising the light emission efficiency and suppressing the variation in illuminance can be realized.

Moreover, according to the backlight device 30 as the third embodiment of the present invention, the same advantages as those of the backlight device 10 according to the first embodiment can be obtained.
Furthermore, the backlight device 30 as the third embodiment of the present invention may be modified and implemented in the same manner as in the first embodiment.

[Light guide plate material and manufacturing method, etc.]
Examples of the material of the light guide plate include glass and transparent resin. The term “transparent” as used herein means that the total light transmittance measured with a 2 mm thick plate smooth on both sides according to JIS K7361-1 is 70% or more. In addition, the material of a light-guide plate may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  As a material for the light guide plate, it is preferable to use a transparent resin. In general, since a resin has a low elastic modulus, when a thin light guide plate is manufactured using a transparent resin, the light guide plate usually has flexibility. For this reason, for example, when a backlight device is provided in a display device, even when local heating occurs due to a light source, an auxiliary circuit, or the like, a phenomenon of locally pushing the display panel of the display device hardly occurs. Therefore, when the backlight device is provided in the display device, it is possible to prevent the light from passing through. Here, the above-mentioned light removal refers to a phenomenon in which optical contact occurs on the display surface of the display device and the illuminance increases locally.

  Usually, the resin comprises a polymer. Examples of the polymer contained in the transparent resin include propylene-ethylene copolymer, polystyrene, (meth) acrylic acid ester-aromatic vinyl compound copolymer, polyethylene terephthalate, terephthalic acid-ethylene glycol-cyclohexanedimethanol copolymer. Examples thereof include polymers, polycarbonates, methacrylic polymers, and polymers having an alicyclic structure (for example, norbornene-based polymers). Among these, a polymer having an alicyclic structure, a methacrylic polymer, and a (meth) acrylic acid ester-aromatic vinyl compound copolymer are preferable, and a polymer having an alicyclic structure is particularly preferable.

  A polymer having an alicyclic structure has good fluidity in a molten state. Therefore, for example, when a light guide plate is manufactured by injection molding, the mold cavity can be filled with a low injection pressure, so that a thin light guide plate can be formed relatively easily and weld lines are not easily generated. Moreover, when manufacturing a light-guide plate by extrusion molding, for example, there is little thickness nonuniformity at the time of shaping | molding, and the shaping | molding after shaping | molding is easy. Furthermore, since the polymer having an alicyclic structure has extremely low hygroscopicity, it has excellent dimensional stability and is less likely to warp the light guide plate. Furthermore, since the polymer having an alicyclic structure has a small specific gravity, the light guide plate can be reduced in weight.

Examples of the polymer having an alicyclic structure include a polymer having an alicyclic structure in the main chain or side chain. Among them, a polymer having an alicyclic structure in the main chain is particularly suitable because it has good mechanical strength and heat resistance.
The alicyclic structure is preferably a saturated cyclic hydrocarbon structure. The number of carbon atoms constituting the alicyclic structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, and particularly preferably 15 or less. Furthermore, the ratio of the repeating unit having an alicyclic structure in the polymer having an alicyclic structure is preferably 50% by weight or more, more preferably 70% by weight or more, and 90% by weight or more. More preferably it is.

  Examples of the polymer having an alicyclic structure include a ring-opening polymer or a ring-opening copolymer of a norbornene monomer or a hydrogenated product thereof; an addition polymer or an addition copolymer of a norbornene monomer Or a hydrogenated product thereof; a polymer of a monocyclic cycloolefin monomer or a hydrogenated product thereof; a polymer of a cyclic conjugated diene monomer or a hydrogenated product thereof; a vinyl alicyclic hydrocarbon monomer Or a hydrogenated product thereof, a polymer of a vinyl aromatic hydrocarbon monomer or a hydrogenated product of an unsaturated bond part containing an aromatic ring of the copolymer, and the like. Among these, hydrogenated products of norbornene-based monomer polymers and hydrogenated products of unsaturated bonds including aromatic rings of vinyl aromatic hydrocarbon-based monomer polymers have mechanical strength and heat resistance. It is particularly suitable because of its excellent properties.

  Furthermore, among the above preferred polymers, the methacrylic polymer is excellent in transparency, tough and hardly cracked, and therefore can be suitably used. Examples of such a resin containing a methacrylic polymer include a methacrylic resin molding material containing 80% or more of a methyl methacrylate polymer defined in JIS K6717. Among the methacrylic resins specified in this standard, a resin with a specified classification code 100-120 having a Vicat softening point temperature of 96 to 100 ° C. and a melt flow rate of 8 to 16 has an appropriate fluidity and strength, and thus is particularly suitable. It is.

  The light guide plate material may contain an antioxidant in order to prevent oxidative degradation and thermal degradation during molding. Examples of the antioxidant include a phenolic antioxidant, a phosphorus antioxidant, and a sulfur antioxidant. Of these, phenolic antioxidants are preferred, and alkyl-substituted antioxidants are particularly preferred. In addition, an antioxidant may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. The amount of the antioxidant is preferably 0.01 parts by weight or more, more preferably 0.02 parts by weight or more, preferably 2 parts by weight or less, more preferably 1 part by weight with respect to 100 parts by weight of the polymer component. Or less.

  The material of the light guide plate may contain a light resistance stabilizer in order to improve the light resistance of the light guide plate. Examples of the light resistance stabilizer include hindered amine light resistance stabilizer (HALS) and benzoate light resistance stabilizer. Among these, hindered amine light resistance stabilizers are preferred. In addition, a light-resistant stabilizer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The amount of the light stabilizer is preferably 0.01 parts by weight or more, more preferably 0.02 parts by weight or more, and particularly preferably 0.05 parts by weight or more, preferably 100 parts by weight of the polymer component. It is 2 parts by weight or less, more preferably 1 part by weight or less, and particularly preferably 0.5 part by weight or less.

  The material of the light guide plate may further contain an optional additive as necessary. Examples of additives include stabilizers such as heat stabilizers, ultraviolet absorbers and near infrared absorbers; resin modifiers such as lubricants and plasticizers; colorants such as dyes and pigments; antistatic agents and light diffusing agents. Etc. In addition, an additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  As the light guide plate, for example, a light guide plate having a refractive index of 1.53 (critical angle 40.7 °) may be used.

  When the light guide plate is made of resin, the light guide plate may cause a dimensional change (elongation or warpage) due to moisture absorption. If a dimensional change occurs, wrinkles and the like may occur, and optical characteristics may be impaired. In particular, when the size of the light guide plate is large (for example, 40 inches), the relative positional relationship between the light source and the light introduction surface changes in the backlight device due to the size change, and the light utilization efficiency tends to decrease. is there. For this reason, the water absorption rate of the light guide plate is preferably 0.50% or less, more preferably 0.25% or less, and even more preferably 0.05% or less. The water absorption rate in the present specification is a desiccator after drying a test piece having a disk shape of 50 mm in diameter or a square of 50 mm on a side at 50 ° C. for 24 hours in accordance with JIS K7209 A method. It can be obtained from the weight increase when it is allowed to cool in water and immersed in water at 23 ° C. for 24 hours.

  The material for forming the light guide plate is preferably excellent in heat resistance. Specifically, the Vicat softening temperature is preferably 90 ° C. or higher, more preferably 100 ° C. or higher, and particularly preferably 110 ° C. or higher. If the heat resistance of the light guide plate forming material is low, the light guide plate may be melted or deformed by heat generated from a light source or the like, and optical characteristics may be impaired. The Vicat softening temperature can be measured by the method defined in JIS K7206B.

  Although there is no restriction | limiting in the manufacturing method of a light-guide plate, For example, when forming a light-guide plate with resin, it can manufacture by injection molding method and extrusion molding method.

[Adhesive materials]
As the material of the bonding portion, a material that can transmit light guided through the light guide plate and can bond the light guide plate and the optical film is used. For example, an adhesive may be used as the material for the bonding portion. This adhesive is not only an adhesive in a narrow sense (a so-called hot melt type adhesive having a shear storage elastic modulus of 1 to 500 MPa at 23 ° C. and does not exhibit tackiness at room temperature), but also a shear storage elasticity at 23 ° C. It also includes an adhesive having a rate of less than 1 MPa.

  Examples of the adhesive include water-based adhesives, solvent-based adhesives, two-component curable adhesives, ultraviolet curable adhesives, and pressure-sensitive adhesives. Although there is no restriction | limiting in particular in the selection of an adhesive agent, Usually, an adhesive agent with high transparency is used. In addition, in order to shorten the manufacturing process time, an adhesive whose physical properties do not change immediately after bonding or an adhesive that quickly cures (for example, a hot-melt adhesive, an ultraviolet curable adhesive, an electron beam curable adhesive, etc.) ) Is preferred. Furthermore, in order to ensure the reliability and mechanical strength of the product, an ultraviolet curable adhesive and an electron beam curable adhesive are particularly preferable. Examples of adhesives include acrylic, urethane, polyester, polyamide, polyvinyl ether, polyvinyl alcohol, polyvinyl acetal, polyvinyl formal, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylene-vinyl acetate, ethylene-acrylic ester And synthetic rubbers such as ethylene-vinyl chloride and styrene-butadiene-styrene, and epoxy and silicone adhesives. In addition, an adhesive agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  An additive may be included in the adhesive. Examples of the additive include fine particles having a light beam direction changing function. Examples of such fine particles include white reflective materials such as diffusion beads and fillers formed of a material having a refractive index different from that of the base polymer of the adhesive. Specific examples include inorganic fillers such as glass, silica, aluminum hydroxide, aluminum oxide, titanium oxide, zinc oxide, barium sulfate, magnesium silicate, and mixtures thereof; acrylic resin, polyurethane resin, polyvinyl chloride resin, polystyrene Organic fillers such as resins, polyacrylonitrile resins, polyamide resins, polysiloxane resins, melamine resins, benzoguanamine resins, fluororesins, polycarbonate resins, silicone resins, polyethylene resins, ethylene-vinyl acetate copolymers, acrylonitrile, and cross-linked products thereof Etc. Among these, as the organic filler, an acrylic resin, a polystyrene resin, a polysiloxane resin, and fine particles made of a crosslinked product thereof are preferable in terms of high dispersibility, high heat resistance, and no coloration (yellowing) during molding. . Among these, fine particles made of a crosslinked product of an acrylic resin are more preferable in terms of more excellent transparency. These fine particles may be made of two or more kinds of materials, or two or more kinds of fine particles may be used in combination.

  It is preferable that the material of the bonding portion is not so different in the difference between the refractive index of the bonding portion after curing and the refractive index of the light guide plate and the optical film to be bonded. When the difference in refractive index is large, total reflection occurs at the interface between the light guide plate and the adhesive portion and the interface between the adhesive portion and the optical film, and light may not enter the adhesive portion. Accordingly, the refractive index difference between the adhesive portion and the light guide plate and the optical film is usually 0.5 or less, preferably 0.2 or less. Among these, it is particularly preferable that the refractive index of the bonded portion is higher than the refractive index of the light guide plate and lower than the refractive index of the optical film.

  The material of the bonding portion may be transparent at the time of curing, but may have haze. When the bonding portion has haze, a light diffusion effect by the bonding portion itself can be expected. For example, when using a diffusion film, a prism film, a retroreflective brightness improving film, a reflective sheet, a polarizing film, etc. as an optical film, the material of the adhesive part may have haze, especially when using a polarizing film. It is preferable to have haze.

[Types and physical properties of optical films]
As the optical film, any optical film that can transmit light may be used. Moreover, as an optical film, if it is the one main surface of a light-guide plate, you may use the film which does not permeate | transmit light like a reflective sheet. Furthermore, the optical film may be a single-layer film composed of only one layer, or may be a laminated film having two or more layers.
Examples of the optical film include a diffusion film, a prism film, a retroluminance enhancement film, a polarizing film, and a retardation film. In addition, the reflective sheet in the third embodiment may be a substantially white reflective sheet. For example, the film has fine bubbles in the film and reflects by total reflection at the interface of the bubbles, or includes various fillers and has total reflection performance. You may have. However, if the metallic reflection sheet and the light guide plate are bonded together, there is a risk of warping or the like due to the temperature rise of the entire backlight device during lighting and the difference in coefficient of linear expansion. From this viewpoint, when a polymer material is used for the light guide plate, it is preferable to use a reflective sheet based on a polymer material having a linear expansion coefficient of about 7 × 10 ⁻⁵ / K.

  As a material for the optical film, a resin is usually used, and a thermoplastic resin is preferably used. Examples of polymers contained in the resin include olefin polymers such as polyethylene and polypropylene, polyester polymers such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polyarylene sulfide polymers such as polyphenylene sulfide, and polyvinyl alcohol heavy polymers. Polymer, polycarbonate polymer, polyarylate polymer, cellulose ester polymer, polyethersulfone polymer, polysulfone polymer, polyallyl sulfone polymer, polyvinyl chloride polymer, norbornene polymer, rod-like liquid crystal polymer, styrene or styrene Polystyrene polymers including homopolymers of derivatives or copolymers with other monomers, polyacrylonitrile polymers, polymethylmethacrylate polymers, or multicomponent copolymers thereof. Such as if the polymer, and the like. Further, the resin may contain an additive as necessary. In addition, the material of an optical film may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Regarding the transparency of the optical film, the total light transmittance and haze cannot be defined unconditionally due to the anisotropy and retroreflectivity of each optical film, but if it is an optical film generally used in a backlight device, its Many can be used.

[Method for producing light guide member]
Although there is no limitation on the method of manufacturing the light guide member, usually, a long light guide plate, a long optical film, and, if necessary, another long optical film are prepared. After adhering the material of the adhesive part to the main surface and bonding the light guide plate and the optical film, the light guide member is cut out in a desired shape and size from the obtained long multilayer film. Hereinafter, this manufacturing method will be described with reference to the drawings.

  FIG. 10 is a diagram schematically illustrating an example of a method for manufacturing the light guide member. As shown in FIG. 10, in the method of this example, a long optical film (a reflection sheet in this example) 910, a long light guide plate 920, and a long optical film 930 are prepared. Here, “long” refers to a film having a length of at least 5 times the width of the film, preferably 10 times or more, specifically a roll shape. It has a length enough to be wound up and stored or transported.

  As shown by the arrow X1, the long reflective sheet 910 is continuously conveyed in the long direction (usually coincides with the vertical direction and the MD direction). An adhesive is printed from the printing device 941 on the main surface 911 of the conveyed long reflective sheet 910 to form an adhesive portion 951. The print pattern at this time is set so that the formula I is satisfied in the light guide member 960. Although there is no restriction | limiting in the printing method, As a preferable example, silk screen printing, inkjet printing, etc. are mentioned.

  Thereafter, the reflection sheet 910 on which the adhesive portion 951 is formed is sent between a pair of opposing rolls 971 and 972. Further, a long light guide plate 920 is conveyed between the rolls 971 and 972 as indicated by an arrow X2. The long reflective sheet 910 and the long light guide plate 920 are bonded by the bonding portion 951 by being sandwiched between the rolls 971 and 972.

  At the time when the reflection sheet 910 and the light guide plate 920 are bonded, the bonding portion 951 may not be cured. In this case, it is preferable to cure the adhesive portion 951 by performing treatments such as drying, heating, and ultraviolet irradiation as necessary.

  The bonded reflection sheet 910 and light guide plate 920 are conveyed to the printing apparatus 942. The printing apparatus 942 forms an adhesive portion 952 by printing an adhesive on the main surface 921 of the light guide plate 920 opposite to the main surface bonded to the reflective sheet 910. Also in this case, the print pattern is set so that the formula I is satisfied in the light guide member 960.

  The light guide plate 920 and the reflection sheet 910 in which the bonding portion 952 is formed on the main surface 921 are sent between a pair of opposed rolls 973 and 974. In addition, a long optical film 930 is also sent between the rolls 973 and 974, and is sandwiched between the rolls 973 and 974, so that the light guide plate 920 and the optical film 930 are bonded by an adhesive portion 952. Glued.

  Thereafter, the bonding portion 952 is cured by performing treatments such as drying, heating, and ultraviolet irradiation as necessary. Thereby, a long multilayer film 980 in which the reflection sheet 910, the light guide plate 920, and the optical film 930 are bonded by the bonding portions 951 and 952 is obtained. A light guide member 960 is obtained by punching the long multilayer film 980 with a punching device 990 in a desired shape and size.

As described above, since the light guide member of the present invention functions as a light output portion for extracting light from the light guide plate, the adhesive portion and the light output portion need to be provided separately when the light guide member is manufactured. In addition, the manufacturing efficiency can be improved by reducing the number of manufacturing steps.
In addition, since the light guide member in which the light guide plate and the optical film are bonded together can be manufactured using a long film, it is possible to perform the roll-to-roll bonding, and from the laminated multilayer film Since the light guide member can be manufactured by punching, the manufacturing efficiency can also be improved in this respect.

〔light source〕
Examples of the light source include an LED, a laser diode, a cold cathode tube (CCFL, EEFL), a hot cathode tube (HCFL), and a point light source is preferably used. Any point light source may be used as long as a sufficient amount of light can be obtained. For example, a semiconductor laser or the like may be used. However, it is usually preferable to use an LED as described in the above embodiment. Examples of the LED include a blue-yellow pseudo white light emitting diode, a three-color (RGB) type white light emitting diode, and the like.

  As the LED, for example, a side-emitting LED, a surface-mounted LED, a bullet-type LED, or the like is used. The dimension of the light emitting part of the LED can be set according to the light distribution characteristic of the LED. Usually, the width and height of the light emitting part of the LED are made equal. However, when the LED has an elliptical or oval cross section, the LED having a different width and height may be used. Good.

  A general high dome type LED has a light distribution of Lambertian and emits a relatively large divergent light having a half-value angle (half-value full angle) of about 120 °. However, from the viewpoint of introducing more of the light emitted from the light source into the light guide plate, the full width at half maximum of the LED is preferably 80 ° or less, more preferably 70 ° or less, and particularly preferably 60 ° or less. Ideally, LEDs that emit as close to parallel light as possible are preferred. Further, from the viewpoint of suppressing darkening of the portion corresponding to between the LEDs near the light introduction surface of the light guide plate, the full width at half maximum of the LED is preferably 90 ° or more, more preferably 100 ° or more, and 110 It is particularly preferable that the angle is at least.

  In addition, as a light source, you may use combining light emitting elements, such as LED, and optical elements, such as a lens. For example, even when an LED having a wide full width at half maximum is used, a light source that emits light at a full width at half maximum within the above-described preferable range can be realized by combining the LED and the lens.

[Use]
The backlight device of the present invention is suitable as a device that supplies light to a liquid crystal panel of a liquid crystal display device, for example.
The liquid crystal panel is a member in which, for example, an alignment film, a transparent electrode, a glass plate, a color filter, a polarizing plate, and the like are stacked and arranged at appropriate positions with a liquid crystal layer interposed therebetween. When the backlight device of the present invention is applied to a liquid crystal display device, the backlight device of the present invention is usually provided on the back side of the liquid crystal panel so that light can be supplied to the liquid crystal panel from the back side.
Furthermore, you may make it provide arbitrary optical films between a liquid crystal panel and a backlight apparatus as needed.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and may be arbitrarily changed without departing from the gist of the present invention and its equivalent scope. May be implemented.

[Example 1]
FIG. 11 is a diagram for explaining simulation conditions set in the simulation performed in the first embodiment. In the following examples, an optical model was created and simulated under the conditions described later using optical simulation software “LightTools” (manufactured by Cybernet Co., Ltd.).
In addition, as a material for the light guide plate, a thermoplastic alicyclic structure-containing resin (trade name: ZEONOR1420, manufactured by Nippon Zeon Co., Ltd., refractive index: 1.533, critical angle: 40.7 °, water absorption: 0.01%) Was set. Moreover, as a material of an adhesion part, it set as what used the acrylic adhesive (brand name Nisset KP1954, Nippon Carbide make). Furthermore, as an optical film, it was set as what used the diffusion film (Brand name D-124U, the Tsujiden company make).

  As shown in FIG. 11, a rectangular flat light guide plate was set as the light guide plate 1. The surfaces of the light guide plate 1 are all flat surfaces (arithmetic average roughness Ra = 0.02 μm). The dimensions of the light guide plate 1 are vertical = 100 mm and horizontal (distance between light introduction surfaces) L = 1000 mm. did. Further, three cases of thickness T of 1.0 mm, 0.5 mm and 0.3 mm were set.

  An adhesive portion (not shown) is formed on one main surface 2 of the light guide plate 1 by screen printing so as to have the occupation ratio shown in Table 1 according to the distance from the light introduction surfaces 3 and 4 corresponding to the side surfaces. Was formed. In addition, in the portion between the positions where the set values are shown in Table 1, the occupation ratio was set so as to be gradation every 50 mm in width. At this time, the bonded portion was cylindrical, and the diameter of the bottom side of the bonded portion was set to 0.05 mm and the height was 0.025 mm. Further, an optical film (not shown) was bonded to the main surface 2 on which the bonded portion of the light guide plate 1 was formed by the bonded portion. Further, no adhesive portion is formed on the other main surface of the light guide plate 1.

  The light sources 5 and 6 are provided in front of the light introduction surfaces 3 and 4 corresponding to the side surfaces of the light guide plate 1. As the light sources 5 and 6, a plurality of LEDs (2.5 mm in length, 1.5 mm in width, 0.5 mm in thickness) mounted on a 5 mm wide substrate along the light introduction surfaces 3 and 4 are set. did. The distance from the light introduction surfaces 3 and 4 to the light emitting portions of the light sources 5 and 6 was 2.5 mm. The absorption of the light emitting part of the LED was 15%, and the full width at half maximum was 120 °.

  From the light introduction surfaces 3 and 4 of the light guide plate 1 to the ends of the substrates of the light sources 5 and 6, it was set as covered with a lamp cover (not shown). The reflection on the inner surface of the lamp cover was Lambert reflection with a reflectance of 98%.

  The light output efficiency and the standard deviation σ of the illuminance at each point on the main surface of the optical film when the light introduction surfaces 3 and 4 were irradiated with light from the light sources 5 and 6 in the above configuration were calculated by simulation. The results are shown in Table 1. Further, the distance A from one light introduction surface 3, the distance L between the light introduction surface 3 and the light introduction surface 4, the thickness T of the light guide plate 1, and the occupation ratio of the adhesive portion in the main surface 2 of the light guide plate 1 The relationship of the total S is shown in FIG. 12 for portions where the distance A is 0 mm, 100 mm, 200 mm, 300 mm, 400 mm, and 500 mm.

[Example 2]
Standards of light output efficiency and illuminance at each point on the main surface of the optical film in the same manner as in Example 1 except that the setting of the total occupation S of the main surface 2 of the light guide plate 1 is changed as shown in Table 2. The deviation σ was calculated by simulation. This light exit ratio S satisfies the formula I in a portion excluding 10% in the vicinity of both light incident ends (that is, a portion where A / L = 10% to 50%). The results are shown in Table 2. FIG. 13 shows the relationship between the distance A, the distance L, the thickness T, and the total occupation ratio S for the portions where the distance A is 0 mm, 100 mm, 200 mm, 300 mm, 400 mm, and 500 mm.

Example 3
Table 3 shows the setting of the total L of the occupation ratio of the main surface 2 of the light guide plate 1 that the distance L between the light introduction surfaces 3 and 4 is 600 mm by changing the horizontal dimension of the light guide plate 1. Except for the changes as shown, the light output efficiency and the standard deviation σ of the illuminance at each point on the main surface of the optical film were calculated by simulation in the same manner as in Example 1. This light exit ratio S satisfies the formula I in a portion excluding 17% in the vicinity of both light incident ends (that is, a portion of A / L = 33% to 50%). The results are shown in Table 3. Further, FIG. 14 shows the relationship between the distance A, the distance L, the thickness T, and the total occupation ratio S for the portions where the distance A is 0 mm, 100 mm, 200 mm, and 300 mm.

Example 4
Table 4 shows the setting of the total L of the occupation ratio of the main surface 2 of the light guide plate 1 that the distance L between the light introduction surfaces 3 and 4 is 600 mm by changing the horizontal dimension of the light guide plate 1. Except for the changes as shown, the light output efficiency and the standard deviation σ of the illuminance at each point on the main surface of the optical film were calculated by simulation in the same manner as in Example 1. The results are shown in Table 4. FIG. 15 shows the relationship between the distance A, the distance L, the thickness T, and the total occupation ratio S for the portions where the distance A is 0 mm, 100 mm, 200 mm, and 300 mm.

[Comparative Example 1]
Standards of light output efficiency and illuminance at each point on the main surface of the optical film in the same manner as in Example 1 except that the setting of the total occupation S of the main surface 2 of the light guide plate 1 was changed as shown in Table 5. The deviation σ was calculated by simulation. The results are shown in Table 5. FIG. 16 shows the relationship between the distance A, the distance L, the thickness T, and the total occupation ratio S for the portions where the distance A is 0 mm, 100 mm, 200 mm, 300 mm, 400 mm, and 500 mm.

[Comparative Example 2]
Standards of light output efficiency and illuminance at each point on the main surface of the optical film in the same manner as in Example 1 except that the setting of the total occupation S of the main surface 2 of the light guide plate 1 is changed as shown in Table 6. The deviation σ was calculated by simulation. The results are shown in Table 6. FIG. 17 shows the relationship between the distance A, the distance L, the thickness T, and the total occupation ratio S for the portions where the distance A is 0 mm, 100 mm, 200 mm, 300 mm, 400 mm, and 500 mm.

[Comparative Example 3]
Table 7 shows the setting of the total L of the occupation ratio of the main surface 2 of the light guide plate 1 that the distance L between the light introduction surfaces 3 and 4 is 600 mm by changing the horizontal dimension of the light guide plate 1. Except for the changes as shown, the light output efficiency and the standard deviation σ of the illuminance at each point on the main surface of the optical film were calculated by simulation in the same manner as in Example 1. The results are shown in Table 7. FIG. 18 shows the relationship between the distance A, the distance L, the thickness T, and the total occupation ratio S for the portions where the distance A is 0 mm, 100 mm, and 200 mm.

〔Consideration〕
As can be seen from Tables 1 to 7, in the light guide members of Examples 1 to 4 that satisfy Formula I in the portion where the A / L of the main surface of the light guide plate is 20% to 50%, high light output efficiency and illuminance Both of these can be achieved. On the other hand, the illuminance variation is large in Comparative Examples 1 and 3, and the light output efficiency is not sufficiently high in Comparative Example 2. Therefore, it was confirmed that high light output efficiency and suppression of illuminance variation can be compatible only when Expression I is satisfied.

DESCRIPTION OF SYMBOLS 1 Light guide plate 2 Main surface of light guide plate 3, 4 Light introduction surface 5, 6 Light source 10, 20, 30 Backlight device 100 Light guide member 210, 220 Light source 300 Light guide plate 310 Front surface (main surface) of light guide plate
320 Back surface (main surface) of light guide plate
330 Side surface of light guide plate (light introduction surface)
340 Side surface of light guide plate 350 Side surface of light guide plate (light introduction surface)
360 Side surface of light guide plate 370 Portion where front surface adhesive portion of light guide plate is not formed (interface between light guide plate and air layer)
400 Adhesive part 410 The part where the adhesive part of the front surface of the light guide plate is formed (interface between the light guide plate and the adhesive part)
420 Interface between Adhesion and Optical Film 500 Optical Film 510 Main Surface of Optical Film 520 Main Surface of Optical Film Opposite to Light Guide Plate 600 Adhesion 610 Interface between Adhesion and Light Guide Plate 620 Adhesion and Reflection Sheet Interface 700 Optical film 710 Main surface of optical film 800 Reflective sheet 810 Main surface of reflective sheet 910 Long reflective sheet 911 Main surface of long reflective sheet 920 Long light guide plate 921 Main surface of long light guide plate 930 long optical film 941, 942 printing apparatus 951, 952 adhesion part 960 light guide member 971-974 roll 980 long multilayer film 990 punching apparatus

Claims (3)

A light guide plate having two opposing main surfaces and two opposing light introduction surfaces, an adhesive portion formed on at least one main surface of the light guide plate, and the adhesive portion of the light guide plate formed thereon A light guide member comprising an optical film bonded to the main surface by the adhesive portion,
The thickness of the light guide plate is T (mm), the distance between the two light introduction surfaces facing each other is L (mm), and the light of the two light introduction surfaces facing each other on the main surface is the closest When the total occupancy ratio of the bonded portion per unit area of the two main surfaces facing each other at a portion where the distance to the introduction surface is A (mm) is S (%), the A / In a portion where L is 20% to 50%,

A light guide member that satisfies the requirements. In the part where A / L of the main surface of the light guide plate is 20% to 50%,

The light guide member according to claim 1 satisfying any one of the above.   A backlight device comprising the light guide member according to claim 1.

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