JP2014137520A - Optical diffusion laminate and lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical diffusion laminate capable of enhancing front brightness by the combination of an optical diffusion member and a lens film, reducing patches of the brightness and suppressing poor appearance and angular dependence of emitted light.SOLUTION: The optical diffusion laminate laminated with a first optical diffusion member (A) including one layer consisting of a mixture of two kinds of resin, a lens film (B) having a lens structure formed on one surface and a second optical diffusion member (C) satisfies the following (i) to (iii): (i) a ratio of a total light transmittance to a parallel light transmittance of the internal optical diffusion member (A) is 8 to 110; (ii) a central surface particle size (SGr) of the lens surface of the lens film (B) is 5000 to 30000 μm, and a drop of the degree of emitted light is 3.0 or less at an emission angle of 45 degrees in a deflecting light distribution profile of the emitted light when light is entered at 0 degree; and (iii) a ratio of a total light transmittance to a parallel light transmittance of the second optical diffusion member (C) is 1.0 to 30.

Description

  The present invention is a combination of two light diffusing members and a lens film. When used in a surface light source device, the front luminance and illuminance are high, and luminance spots and illuminance spots can be reduced. Further, the appearance caused by the lens film Light diffusion laminate capable of suppressing appearance defects such as glare and lightness spots, and a drop in emitted light intensity appearing in the vicinity of 45 degrees in the angle dependency of emitted light, while maintaining the above characteristics, and the light diffusion laminate The present invention relates to a surface light source device using a body and an illumination device using the surface light source device.

  Liquid crystal display modules (LCDs) are widely used as flat panel displays taking advantage of their features such as thinness, light weight, and low power consumption, and their uses are for information displays such as mobile phones, personal digital assistants (PDAs), personal computers, and televisions. It is expanding year by year as a device.

  The liquid crystal display device is equipped with a surface light source device on the lower surface side of the liquid crystal unit in order to suppress a loss in the light transmission path from the light source to the panel and improve the luminance on the panel.

  In recent years, surface light source devices have been used not only in liquid crystal display devices but also in a wide range of fields such as lamps and electric signboards.

  In the surface light source device, the basic unit of the surface light source device and various optical films such as a lens film, a light diffusion film and a brightness enhancement film, and optical members such as a light diffusion plate are combined to increase the luminance and illuminance of the surface light source device. In addition, the uniformity of brightness and illuminance is improved. Usually, 2 to 4 optical members are used (see, for example, Non-Patent Document 1).

  In particular, a method using a lens film is widely used. However, in general, when only a lens film is used, the luminance when viewed from the front (hereinafter referred to as front luminance) is improved by the light condensing effect. For example, Patent Document 1 describes the following. The bead coat method light diffusion film, prism lens film, and brightness enhancement film have a problem that the uniformity of brightness within the surface of the surface light source (hereinafter referred to as brightness spots) is inferior. On the other hand, although it is possible to suppress luminance unevenness by using a light diffusing plate having high diffusibility, it is stated that there is a problem that front luminance decreases. That is, it is stated that the relationship between front luminance and luminance spots is a contradictory phenomenon. Furthermore, in Patent Document 1, as a method for achieving both of these characteristics, for example, a method in which three optical members, a light diffusing plate, an anisotropic light diffusing film, and a prism lens film, are combined is disclosed. In this method, a light diffusing plate having a non-spectral total light transmittance as low as 60% is used, and an anisotropic light diffusing film is further combined, so that the total non-spectral total light transmittance of the light diffusing material is reduced. Further, since it is lower, the effect of suppressing luminance unevenness is good, but not only has the problem that the front luminance decreases greatly, but the cell itself also increases in volume, which is not preferable.

  Patent Document 2 discloses a method using a constituent member in which various lens structure surface irregularities are formed on the surface of an internal light diffusing film made of a matrix resin containing a light diffusing element. Patent Document 2 uses a multi-sheet configuration composed of a light diffusing plate, the above light diffusing film, and two other light diffusing films, and has the problem of lowering the front luminance similarly to the method of Patent Document 1. In addition, the cell itself increases in volume, which is not preferable.

  In addition, when a non-prism lens film is used, the effect of the diffusivity of the milky white plate is the greatest on the suppression of luminance unevenness, and a milky white plate having a non-spectral total light transmittance of 50 to 70% is preferred. . In this technique, a light diffusion sheet is further installed on the light exit surface of the lens film. Therefore, there is a problem that the luminance unevenness suppressing effect is good, but the front luminance decrease is large (see, for example, Patent Document 3).

  In addition, a mountain range-type lens film oriented in one direction, such as a prism lens film or a lenticular lens film, is said to be inferior in the isotropy of the light distribution of the emitted light because the emitted light is condensed in a specific direction. Has a problem. Furthermore, there is a problem in that a drop in the emitted light intensity occurs in which the emitted light intensity near the exit angle of 45 degrees is reduced. As a method for solving these problems, for example, there is a technique of a lens film having a composite structure in which two or more types of lens structures are combined, such as a combination of a first lens structure and a second lens structure in an intersecting direction. (For example, refer to Patent Documents 4 to 7).

  In the case of the lens film having such a structure, the light diffusion member is indispensable because the light diffusion degree is insufficient as in the case of the conventional lens film. For example, in Patent Document 4, a light diffusing plate is used. In Patent Documents 5 and 6, a light diffusing plate having a non-spectral total light transmittance of 65% is used. Further, in Patent Document 6, both a light diffusion plate and a light diffusion film are used. Accordingly, the techniques disclosed in these patent documents also have the same problems as those in Patent Documents 1 and 2. In Patent Document 7, a brightness enhancement film is used in addition to the optical member.

  For technologies using widely used prism lens films and lenticular lens films, as a method to achieve both front brightness and brightness spots, the reduction in front brightness due to the light diffusing material used to improve brightness spots As a method for solving the problem, a method of using two lens films and a method of a multi-sheet configuration using a brightness enhancement film are disclosed (for example, see Patent Documents 8 to 11).

  However, as in Patent Documents 1 to 7, it is not a fundamental solution as a method for achieving both front luminance and luminance spots, but the volume of the cell itself increases, and lens films and luminance enhancement films are expensive. It is economically inferior.

  In addition, many techniques that combine various optical members in order to achieve both high brightness and low brightness spots have been disclosed, but problems remain in achieving both performance and economy.

  In recent years, with the rapid spread of display devices using surface light source devices, there is a strong demand for surface light source devices with higher brightness and improved in-plane uniformity of brightness and angle dependency of brightness.

  On the other hand, the method using a lens film can give high light condensing performance, so that the brightness and illuminance of the front can be increased. However, when the lens film is installed on the outermost surface, the lens structure of the lens film when viewed obliquely. There is a problem that glare and interference spots caused by. Further, when the lens film is used, the present inventors, for example, when the surface light source device is turned on in a dark room, various patterns such as oblique, horizontal, or arcuate brightness spots on the dark room wall. I found out. The brightness spot pattern varies depending on the method of the light source device used. Hereinafter, the brightness spots are collectively referred to as brightness spots.

  Conventionally, a lens film has been mainly used in a backlight device for a display device. Among these problems, various improvement techniques have been disclosed for the suppression of interference spots. There are few technical disclosures. In particular, regarding brightness spots, no technical disclosure has been found that touches the phenomenon itself within the knowledge of the present inventors. In the case of development as a light source device for illumination which is expected to make great progress in the future, it is considered essential to suppress glare.

  As a method of suppressing the glare of the lens film, a method of making the lens structure of the lens film a specific structure is disclosed (for example, see Patent Document 12). However, the method of changing the lens structure may be difficult to achieve both the light condensing property by the lens structure, and the development of a method for suppressing glare without changing the lens structure is desired.

  In addition, as a method for suppressing glare, which is used for a liquid crystal display device, in a liquid crystal display device in which a backlight is disposed under the liquid crystal display element, a gap between the light diffusion plate constituting the backlight and the liquid crystal display element is used. In addition, a lens film having a prism surface on the upper surface and a substantially smooth surface on the lower surface is disposed, and between the lens film and the liquid crystal display element, the upper surface is a rough surface by embossing and the lower surface is a substantially smooth surface. A method of disposing a second light diffusing plate is disclosed (see Patent Document 13).

  However, in this method, light diffusion plates are installed on both surfaces of the lens film, and the effect of suppressing glare is good, but it is assumed that the front luminance and illuminance are low.

JP 2009-43639 A JP 2010-249898 A JP 2008-60013 A JP 2011-64903 A JP 2010-160437 A JP 2009-75366 A JP 2011-90299 A JP 2010-176086 A Japanese Patent Laid-Open No. 06-222207 WO08 / 90821 JP 2010-157384 A JP 2010-117394 A Japanese Patent Laid-Open No. 06-34972

Supervised by Tatsuo Uchida “All about Illustrated Electronic Display” (published by Industrial Research Association) P47-48

  The object of the present invention is to solve the above-mentioned problems in the prior art, and when used in a surface light source device, the combination of the light diffusing member and the lens film has high front luminance and illuminance, and the luminance and The above characteristics can be maintained by reducing the unevenness of illuminance and causing the appearance glare and brightness irregularities caused by the lens film, and the occurrence of a drop in the intensity of the emitted light that appears near 45 degrees in the angle dependence of the emitted light. It is providing the light-diffusion laminated body which can be suppressed in the shape. Moreover, it is providing the surface light source device using this light-diffusion laminated body, and the illuminating device using the surface light source device.

  In order to solve the above problems, the present invention has been completed by adopting a new concept that is not found in the prior art. In other words, in the prior art, luminance unevenness has been suppressed by using a light diffusing plate having a high light diffusivity or a combination of a plurality of light diffusing members. Has a problem of lowering, and so-called antinomy event could not be overcome.

  Therefore, the inventors of the present invention have found that the light diffusing member alone has a low light diffusivity and has little effect of reducing luminance spots, and has a moderate light diffusing degree and a combination of a lens film having a specific structure. It has been found that by reducing the luminance spots due to the synergistic effect of the light diffusivity, it is possible to achieve both high front luminance and low luminance spots, and to overcome the above-mentioned antinomy event.

  Furthermore, the present invention has established a new characteristic value that accurately reflects the light diffusivity, which is unprecedented, such as the ratio of total light transmittance / parallel light transmittance, and has set it in a range that could not be adopted conventionally.

  And by using the specific light diffusing member also on the lens surface side of the lens film, appearance defects such as roughness of appearance and brightness spots were prevented.

That is, this invention consists of a structure of (1)-(4).
(1) a first light diffusing member (A) including at least one layer composed of a mixture of at least two kinds of resins that are incompatible with each other, a lens film (B) having a lens structure formed on one side, and a second light The diffusing member (C) is in contact with the lens surface of the lens film (B) and the second light diffusing member (C), and the opposite surface of the lens surface of the lens film (B) and the first light diffusing member (A) Are laminated so that the surface of the first light diffusing member (A) is in contact with the surface of the light source surface of the surface light source device, the first light diffusing member (A ), The lens film (B), and the second light diffusion member (C) satisfy the following (i) to (iii):
(I) The first light diffusing member (A) has a total light transmittance / parallel light transmittance ratio of 8 to 110,
(Ii) The lens surface (Gr) has a center surface particle size (SGr) of 5000 to 30000 μm ² and an incident angle of 45 degrees in the variable-angle light distribution profile of the emitted light when incident at 0 degree. Satisfy simultaneously that the drop in the luminous intensity is 3.0 or less,
(Iii) The total light transmittance / parallel light transmittance ratio of the second light diffusing member (C) is 1.0 to 30.
(2) The light diffusion laminate according to (1), wherein the surface glossiness of the surface of the laminate on the second light diffusion member (C) side is 5 to 80%.
(3) The light diffusing laminate according to (1) or (2) is installed so that the surface on the first light diffusing member (A) side is in contact with the surface on the light emitting surface side of the surface light source device. A surface light source device.
(4) A lighting device comprising the surface light source device according to (3).

  The light diffusing laminate of the present invention comprises a laminate in which two light diffusing members having specific different characteristics are respectively arranged above and below a lens film having a specific structure and characteristics, and this is used as the light output of the surface light source device. By installing on the side, the light emission efficiency and the uniformity thereof are enhanced, so that the planar light source device can be increased in luminance and illuminance, and the uniformity of luminance and illuminance can be increased. Furthermore, it is possible to improve the appearance defects such as glare of the light exit surface caused by the lens structure of the lens film and the problem of brightness spots.

  In addition, since the lens film used in the light diffusion laminate of the present invention has a specific structure and characteristics, it has a mountain range type structure oriented in one direction such as a commonly used prism lens film or lenticular type. The phenomenon in which the emitted light that emerges is condensed in a specific direction, so-called isotropic degradation of the light distribution profile of the emitted light, and the drop in the emitted light intensity that appears near 45 degrees in the angle dependency of the emitted light. It can suppress in the form which maintained the high light condensing property. Therefore, when the surface light source device of the present invention is used for general illumination, uniform illumination with little directivity can be achieved. Therefore, the light diffusion laminate of the present invention can be suitably used for lighting devices.

It is the figure which showed an example of the preferable lens structure in this invention. It is the figure which showed an example of the preferable lens structure in this invention. It is the figure which showed an example of the preferable lens structure in this invention. It is the figure which showed an example of the preferable lens structure in this invention. It is the conceptual diagram which showed an example of the effect of the lens structure of this invention. In addition, the horizontal axis of this figure is the angle (degree) in the variable angle measurement, and the vertical axis is the relative value of the emitted light intensity. It is the figure which showed an example of the effect of the lens structure of this invention. In addition, the horizontal axis of this figure is the angle (degree) in the variable angle measurement, and the vertical axis is the relative value of the emitted light intensity. It is the conceptual diagram which showed an example of the preferable lens structure in this invention. It is the figure which showed the relationship between the center surface particle size (SGr) of the lens surface of the lens film (B) of the Example of Table 3, and a comparative example, front luminance, and a brightness spot. It is the figure which showed the relationship between the total light transmittance / parallel light transmittance ratio of a 2nd light-diffusion member (C), front luminance, and surface glossiness using the numerical value of the Example of Table 4, and a comparative example.

(Basic structure of light diffusion laminate)
The light diffusing laminate of the present invention comprises a first light diffusing member (A) including at least one layer composed of a mixture of at least two kinds of resins that are incompatible with each other, and a lens film (B) having a lens structure formed on one side. ) And the second light diffusing member (C), the lens surface of the lens film (B) and the second light diffusing member (C) are in contact with each other, and the surface opposite to the lens surface of the lens film (B) and the first light. In the light diffusing laminate that is laminated so as to be in contact with the diffusing member (A), and is installed so that the surface on the first light diffusing member (A) side is in contact with the surface on the light emitting surface side of the surface light source device, The one light diffusing member (A), the lens film (B), and the second light diffusing member (C) satisfy the following (i) to (iii).
(I) The first light diffusing member (A) has a total light transmittance / parallel light transmittance ratio of 8 to 110,
(Ii) The lens surface (Gr) has a center surface particle size (SGr) of 5000 to 30000 μm ² and an incident angle of 45 degrees in the variable-angle light distribution profile of the emitted light when incident at 0 degree. Satisfy simultaneously that the drop in the luminous intensity is 3.0 or less,
(Iii) The total light transmittance / parallel light transmittance ratio of the second light diffusing member (C) is 1.0 to 30.

(Total light transmittance / parallel light transmittance ratio of the first light diffusion member (A))
The first light diffusing member (A) of the present invention needs to have a total light transmittance / parallel light transmittance ratio of 8 to 110.

  The inventors of the present invention have a high light diffusivity for the first light diffusing member (A) in which the lens film (B) and the first light diffusing member (A) are laminated as described later. Instead, it was considered that a desired light diffusivity should be ensured by a synergistic effect with the light diffusivity of the lens film (B) using a material having an appropriate light diffusivity.

As described above, in the surface light source device, a light diffusing material having a high light diffusivity is required to achieve both high luminance and luminance unevenness. The magnitude of the light diffusivity is displayed, for example, by quantifying the spread of the variable angle light distribution profile of the outgoing light measured by a variable angle photometer. In general, it is often indicated by a so-called half-value width light diffusivity, which is an angular width when the intensity is half of the maximum emitted light intensity. Also, the angle from the rising angle of the variable-angle light distribution profile of the emitted light to the return to the zero point, and the ratio of the emitted light intensity at the outgoing angle of 0 degrees and the emitted light intensity at the predetermined outgoing angle are displayed. The present inventors refer to the light diffusivity as the spread of light.
However, it has been found that the optimum range of the light diffusing member of the light diffusing laminate in the present invention cannot be shown by the half-width method light diffusivity and the skirt spread light diffusivity. This is because the light diffusivity measured by these conventionally known methods is affected by the pattern of the variable-angle light distribution profile of the emitted light. Therefore, the light diffusion degree display method of the first light diffusing member (A) in the system in which the first light diffusing member (A) and the lens film (B), which are the basic structure of the light diffusing laminate in the present invention, are laminated. I thought it was not suitable.

  On the other hand, it is not limited by the variable light intensity characteristic, but is controlled by a characteristic value that is not affected by the pattern of the variable light distribution profile measured by a haze meter such as non-spectral total light transmittance, diffuse transmittance, parallel light transmittance, or haze. Some patents have been issued. However, it has been found that these characteristic values are also not suitable for completing the technology based on the above-described new concept.

  In view of this, the present inventors have intensively studied a method for evaluating an appropriate light diffusivity, and have found that the total light transmittance / parallel light transmittance ratio described in detail in Examples is appropriate for representing the light diffusivity.

Since the total light transmittance is a characteristic value obtained by adding the parallel light transmittance and the diffuse transmittance, the total light transmittance / parallel light transmittance ratio, which is a value obtained by dividing the total light transmittance by the parallel light transmittance, is I thought it would be a measure of light diffusivity. That is, the greater the ratio of total light transmittance / parallel light transmittance, the greater the contribution of diffuse transmittance, and the greater the light diffusivity. On the other hand, the widely used haze is diffuse transmittance / total light transmittance × 100, so that both characteristic values are completely different.
It is surprising that the light diffusivity could not be displayed in such a very simple way. In general, it is presumed that the light diffusivity has become a blind spot because the idea that standardized characteristic values such as haze and diffuse transmittance can be evaluated.

The total light transmittance / parallel light transmittance ratio was established by using a double beam spectroscope instead of a widely used haze meter and paying attention to light having a wavelength of 550 nm. This is also an important factor. The reason for paying attention to light having a wavelength of 550 nm is that light having a wavelength near 550 nm is considered to have the highest spectral luminous efficiency for human eyes.
On the other hand, when a non-spectral total light transmittance or parallel light transmittance measured with a haze meter using non-spectral light that has been used in the prior art is used, good results cannot be obtained. It is speculated that this is due not only to the difference between spectroscopic and non-spectral, but also due to the difference in the measuring method of parallel light transmittance between the two measuring methods. This is because the parallel light transmittance measured by the haze meter is obtained by providing an opening in a portion where light incident on the integrating sphere goes straight and measuring the amount of light passing through the opening. Thus, the parallel light transmittance measured with a double beam spectroscope has a difference in measurement method in which the amount of pure straight light is measured without using an integrating sphere. Therefore, it is speculated that this difference in measurement method also has an effect.
Therefore, the completion of the present invention establishes a new characteristic value that accurately reflects the unprecedented light diffusivity of the total light transmittance / parallel light transmittance ratio, and further sets it in a range that could not be adopted conventionally. This is the first time it has been achieved.

In the present invention, the total light transmittance / parallel light transmittance ratio of the first light diffusing member (A) is more preferably 9 to 110, still more preferably 10 to 100, and particularly preferably 11 to 100.
Only when the total light transmittance / parallel light transmittance ratio of the first light diffusing member (A) satisfies 8 to 110, it is possible to achieve both high front luminance and low luminance unevenness. In either case of a high light diffusivity exceeding the above range or a low light diffusivity below the above range, the front luminance becomes low and the luminance unevenness becomes large.
When the total light transmittance / parallel light transmittance ratio is less than 8, the brightness unevenness increases due to insufficient light diffusion. For this reason, a portion having an extremely low emission luminous intensity is generated, and the average luminance is lowered. On the other hand, when the total light transmittance / parallel light transmittance ratio exceeds 110, the light diffusivity becomes too large, so that the emitted light intensity to the front is lowered and the front luminance is lowered. In addition, since the light diffusivity becomes too large, the amount of light emitted in the direction of a large angle becomes excessive, and the amount of light incident on the lens film (B) at this high angle increases to change the light by the lens film (B). It is presumed that the amount of light in the direction of suppressing luminance unevenness is reduced by the change of the synergistic effect with the curvature effect, and the luminance unevenness is rather increased.

  The first light diffusion member (A) of the present invention preferably has a haze of 80 to 98%, more preferably 85 to 98%. 90 to 98% is more preferable. If it is less than 80%, luminance spots become large, which is not preferable. Conversely, it is difficult to produce more than 98%.

  The first light diffusing member (A) of the present invention preferably has a non-spectral total light transmittance of 74 to 95%. 78 to 95% is more preferable, and 80 to 95% is more preferable. If it is less than 74%, the front luminance decreases and the luminance unevenness increases, which is not preferable. On the other hand, a content exceeding 95% is not preferable because luminance spots increase.

  The first light diffusing member (A) of the present invention preferably has a diffused light transmittance of 68 to 90%. 70 to 85% is more preferable. If it is less than 68%, the front luminance decreases and the luminance unevenness increases, which is not preferable. Conversely, it is difficult to produce more than 90%.

(Structure and characteristics of lens film (B))
The lens film (B) of the present invention has a lens surface center particle size (SGr) measured by the method described in the examples of 5000 to 30000 μm ² and is measured by the method described in the examples. A lens structure formed on one side that simultaneously satisfies that the drop in the emitted light intensity at an output angle of 45 degrees in the variable light distribution profile of the emitted light when incident at a degree is 3.0 or less. Features.

  The center plane particle size (SGr) is a value correlated with the surface area of the lens surface measured by a three-dimensional surface roughness meter. That is, it is a value indicated by the sum of the areas of the sliced surfaces of the protrusions when the surface protrusions are horizontally sliced at the position of the average height obtained by the least square method of the surface protrusions by the lens structure.

  The inventors of the present invention laminated the first light diffusing member (A) and the lens film (B) according to the configuration of the present invention, and closely observed the surface of the lens film (B) when installed on the light exit surface of the surface light source device. Then, since the surface of the lens film (B) appears to shine as though it is emitting light, in the configuration of the present invention, the front luminance is greatly influenced by the surface area of the lens structure of the lens film (B). In view of this, the center plane grain size (SGr) was established as a new measure correlated with frontal luminance.

Therefore, when the center plane particle size (SGr) is less than 5000 μm ² , the surface area of the lens film (B) is insufficient, and the front luminance is lowered. On the contrary, if it exceeds 30000 μm ² , it is difficult to economically produce the lens film (B), which is not preferable. Center plane granularity (SGr) is more preferably 6000~30000μm ^2, more preferably 10000~22000μm ^2, 11000~21000μm ² is particularly preferred.

  In addition, the lens film (B) of the present invention has a drop in the emitted light intensity at an emission angle of 45 degrees in the light distribution profile of the emitted light when incident at 0 degrees as measured by the method described in the examples (hereinafter referred to as the following). (It may be simply referred to as a drop in emitted light intensity) is required to be 3.0 or less. 2.0 or less is more preferable, 1.5 or less is more preferable, and 1.1 or less is particularly preferable. The lower limit of the drop in emitted light intensity is not particularly limited, but is preferably 0.1. If it is less than 0.1, the brightness and illuminance at a high angle may decrease.

  By satisfying this characteristic, it is possible to improve the drawback of the generally used prism lens film that the brightness is greatly reduced when observed from an angle of around 45 degrees, that is, the emitted light intensity drops in a so-called oblique direction. . Therefore, when the surface light source device of the present invention is used for general illumination, uniform illumination without a drop in illuminance at a specific angle can be achieved. In addition, when used as a light source of a display device, it is possible to suppress a decrease in viewing angle in a specific direction and a decrease in luminance at a specific angle.

  Therefore, by simultaneously satisfying the above-described center surface particle size and outgoing light intensity drop characteristic of the lens surface, it is possible to improve the disadvantages of the prism lens film while having high front luminance and front illuminance. Furthermore, since luminance spots can be suppressed as shown in the examples and comparative examples, both high front luminance and front luminance and low luminance spots can be achieved.

  The lens film (B) of the present invention is not limited in its lens structure as long as it satisfies the above surface structure characteristics and depression characteristics. However, for example, a mountain range type structure oriented in one direction such as a prism structure or a lenticular structure is not preferable. In the case of this structure, it is difficult to suppress a drop in the emitted light intensity and to provide isotropy. Therefore, for example, a single-peak type structure such as a dome shape or a pyramid shape, a structure in which the single-peak type structure is combined with a mountain range type structure, and a composite structure in which mountain range type structures are combined in a cross or cross shape Is preferred.

  In particular, in the present invention, a composite structure in which two or more types of lens structures are combined is more preferable. For example, a structure in which prism structures having different directions are combined, or a structure in which a mountain range type structure oriented in one direction and a single peak type structure are combined.

Specific examples include the following structures.
The surface lens structure is composed of two lens arrays (X1A and X2A) whose extending directions are substantially orthogonal. Thereby, the visual field in two directions can be controlled symmetrically, and as a result, the visual field in the 360 degree direction can be controlled. Here, the term “substantially orthogonal” refers to an intersection within a range of 70 degrees or more and 90 degrees or less. If the crossing angle is less than 70 degrees, the bi-directional fields to be controlled are tilted, and a symmetrical field of view cannot be obtained.

  Examples of such a lens structure include a pyramid shape as shown in FIG. 1 or an inverted pyramid shape as shown in FIG. The hip roof shape as shown is mentioned. It is desirable that these lens structures have a triangular shape in which the cross-sectional shape in each extending direction is substantially symmetrical. Here, “substantially symmetrical” means that the difference in angle between the base and the two hypotenuses is within a range of 5 degrees. When it exceeds 5 degrees, the visual field characteristics become asymmetrical, which is not desirable.

  On the other hand, as a more preferable lens structure, there is a lens structure in which either one of the top part or the bottom part of the lens array in two directions is coincident and the other is not coincident. Specifically, the first lens array X1A and the second lens array X2A that are smaller than the first lens array X1A as shown in FIG. The first lens array X1A has a substantially symmetric trapezoidal prism shape, the second lens array X2A has a substantially symmetric triangular prism shape, and the second lens array X2A is formed on the top of the first lens array X1A. It has a structure in which the positions of the tops coincide.

  The angle formed between the base and the hypotenuse of the trapezoidal prism array X1A, which is the first lens array X1A, is preferably set in a range of 35 degrees to 55 degrees. If the angle is less than 35 degrees, the lens structure has a low light condensing function in the front direction. On the other hand, if the angle exceeds 55 degrees, side lobes are generated and the light condensing function in the front direction is deteriorated. Furthermore, when it is out of the range, it is difficult to achieve both suppression of luminance unevenness and high luminance. A more preferable angle range is 40 degrees or more and 50 degrees or less, and the most preferable angle is 45 degrees. The side lobe is a characteristic related to the drop in the emitted light intensity.

  It is preferable that the angle formed between the base and the hypotenuse of the triangular prism array X2A that is the second lens array X2A is set in a range of 35 degrees to 55 degrees. If the angle is less than 35 degrees, the lens structure has a low light condensing function in the front direction. On the other hand, if the angle exceeds 55 degrees, side lobes are generated and the light condensing function in the front direction is deteriorated. Furthermore, when it is out of the range, it is difficult to achieve both suppression of luminance unevenness and high luminance. A more preferable angle range is 40 degrees or more and 50 degrees or less, and the most preferable angle is 45 degrees.

  The lens structure of the present invention is characterized in that it is easy to control the viewing angle characteristics in two directions because the first lens array X1A and the second lens array X2A are formed as independent lens arrays. That is, when the width of the top of the trapezoidal prism X1A is reduced, the ratio of the trapezoidal prism array X1A to the surface area of the lens structure increases, and the light collecting function of the trapezoidal prism array X1A is enhanced. On the other hand, when the top of the trapezoidal prism array X1A is enlarged, the ratio of the triangular prism array X2A to the surface area of the lens structure increases, and the condensing function of the triangular prism array X2A is enhanced. In this way, it is possible to adjust appropriately according to desired visual field characteristics.

  The conventional triangular prism structure or trapezoidal prism structure has a problem that side lobes occur when the angle formed between the base and the hypotenuse exceeds 40 degrees. As shown in FIG. 5, a side lobe generates a peak (side lobe) in an oblique direction separately from the condensing peak in the front direction, and there is a dark field between the condensing peak in the front direction and the side lobe. It refers to what happens. The lens structure of the present invention is composed of the trapezoidal prism array X1A and the triangular prism array X2A in which the angle between the base and the hypotenuse is set in the range of 35 degrees to 55 degrees, but no side lobe occurs. The prism has a light collecting function in a direction orthogonal to the extending direction, and does not have a light collecting function in the extending direction. The viewing angle characteristics plotted with circles shown in FIG. 5 are the characteristics (V) in the direction orthogonal to the prism extending direction, and the viewing angle characteristics plotted with X are the characteristics (H) in the prism extending direction. It is. Therefore, the lens structure of the present invention includes two prisms, ie, the first lens array X1A and the second lens array X2A, so that both light collecting functions can be complemented. That is, the light distribution obtained by adding the viewing angle characteristic (V) in the direction orthogonal to the prism and the viewing angle characteristic (H) in the direction parallel to the prism as shown in FIG. 5 can be obtained. As shown in FIG. Here, the viewing angle characteristic diagram shown in FIG. 6 shows that the angle between the base and the hypotenuse of the trapezoidal prism array X1A is 45 degrees, the angle between the base and the hypotenuse of the triangular prism array X2A is 45 degrees, and the surface area of the lens structure. FIG. 5 is a characteristic diagram when the ratio of each lens array is 50%. In this case, both VH viewing angles can be made the same.

  FIG. 7 shows an example of another lens structure according to the present invention in which the positions of the bottoms of the two-direction lens arrays match and the positions of the tops do not match. The lens structure includes a first lens array X1B arranged with a gap and a second lens array X2B arranged to fill the gap and smaller than the first lens array X1B. The first lens array X1B has a substantially symmetrical triangular prism shape, the second lens array X2B also has a substantially symmetrical triangular prism shape, and the position of the bottom of the second lens array X2B is the bottom of the first lens array X1B. It takes a structure that matches the position of.

  The angle formed between the base and the hypotenuse of the triangular prism array X1B, which is the first lens array X1B, is preferably set in a range of 35 degrees to 55 degrees. If the angle is less than 35 degrees, the lens structure has a low light condensing function in the front direction. On the other hand, if the angle exceeds 55 degrees, side lobes are generated and the light condensing function in the front direction is deteriorated. Furthermore, when it is out of the range, it is difficult to achieve both suppression of luminance unevenness and high luminance. A more preferable angle range is 40 degrees or more and 50 degrees or less, and the most preferable angle is 45 degrees.

  The angle formed between the base and the hypotenuse of the triangular prism array X2B, which is the second lens array X2B, is preferably set in a range of 35 degrees to 55 degrees. If the angle is less than 35 degrees, the lens structure has a low light condensing function in the front direction. On the other hand, if the angle exceeds 55 degrees, side lobes are generated and the light condensing function in the front direction is deteriorated. Furthermore, when it is out of the range, it is difficult to achieve both suppression of luminance unevenness and high luminance. A more preferable angle range is 40 degrees or more and 50 degrees or less, and the most preferable angle is 45 degrees.

  Since the first lens array X1B and the second lens array X2B are formed as independent lens arrays, the lens structure of the present invention is characterized by easy control of viewing angle characteristics in two directions. That is, when the gap in which the triangular prism X1B is disposed is reduced, the ratio of the triangular prism array X1B to the surface area of the lens structure increases, and the condensing function of the triangular prism array X1B is enhanced. On the other hand, when the gap in which the triangular prism array X1B is arranged is increased, the ratio of the triangular prism array X2B to the surface area of the lens structure increases, and the light collection function of the triangular prism array X2B is enhanced. In this way, it is possible to adjust appropriately according to desired visual field characteristics. Also in this case, like the lens structure described above, the side lobe does not occur.

  As described above, the lens shape is described as being convex, but in the present invention, a concave shape obtained by inverting the shape may be used. Even if it is this concave shape, the said effect can be expressed.

  By making the lens structure as described above, for example, emitted light that appears in a mountain-type structure oriented in one direction, such as a prism lens film or a lenticular type, is collected in a specific direction while maintaining a high light-condensing effect. That is, it is possible to suppress the so-called isotropic phenomenon of the isotropic distribution of the emitted light distribution profile and the drop of the emitted light intensity that appears around 45 degrees in the angle dependency of the emitted light. Therefore, when the surface light source device of the present invention is used for general illumination, it can lead to an effect that uniform illumination without directionality can be achieved. In addition, when used as a light source of a display device, it is possible to suppress a decrease in viewing angle in a specific direction and a decrease in luminance at a specific angle. In addition, both high front luminance and low luminance spots can be achieved.

  The height, width and interval of the lens structure are not limited. Further, the inclination angle in the case of a structure having an inclined surface and the curvature in the case of having an arc structure are not limited. What is necessary is just to set suitably so that the said surface structure characteristic may be satisfy | filled.

(Isotropic property of lens film (B))
The lens film (B) of the present invention preferably has an isotropic degree of 0.72 to 1 measured by the method described in the examples. 0.75-1.0 is more preferable. When the surface light source device is used for general illumination by satisfying the above range, uniform illumination without directionality can be achieved. In addition, when used as a light source of a display device, it is possible to suppress the occurrence of a decrease in viewing angle in a specific direction, and it is possible to achieve both high front luminance and front luminance and low luminance spots.

(Method for producing lens film (B))
The method for producing the lens film (B) of the present invention is not limited as long as the above characteristics are satisfied. For example, a method of forming a UV curable resin or a radiation curable resin on a translucent substrate, or a substrate Using PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate), COP (cycloolefin polymer), PAN (polyacrylonitrile copolymer), AS (acrylonitrile styrene copolymer), etc. Examples thereof include a method of forming by an extrusion molding method, an injection molding method, or a hot press molding method well known in the technical field.

(Combined characteristic of total light transmittance / parallel light transmittance ratio of light diffusion laminate and total light transmittance)
The light diffusion laminate of the present invention preferably has a total characteristic of 2500 to 4000 of the total light transmittance / parallel light transmittance ratio and the total light transmittance measured by the method described in the examples. 2600-3900 is more preferable. 2600-3800 is more preferable. By satisfying the above range, it is possible to achieve both high luminance and low luminance spots, and achieve high luminance and small luminance spots. In either case of high light diffusivity exceeding the above range or low light diffusivity below the above range, the luminance is low, and the luminance unevenness is large.

(Surface gloss of light diffusion laminate)
In the light diffusion laminate of the present invention, the first light diffusion member (A), the lens film (B), and the second light diffusion member (C) are laminated in this order, and the first light diffusion member (A) is laminated on the lens surface of the lens film (B). Although it has the structure which piled up the two light-diffusion member (C), it is preferable that the surface glossiness of the surface at the side of the 2nd light-diffusion member (C) of a laminated body is 5 to 80%. More preferably, it is 5 to 70%, and particularly preferably 6 to 60%. When the surface glossiness exceeds 80%, glare in appearance and lightness spots may occur. Conversely, if it is less than 5%, the effect of improving the appearance defect is saturated, and the front luminance and illuminance may be reduced.
As described above, the specific lens film (B) of the present invention can solve the drawbacks of the prism lens film, such as the drop in brightness and illuminance at a specific angle and the direction dependency of the characteristics. Due to the lens structure of the film, glare in appearance and unevenness in brightness are generated. Therefore, when used as, for example, a lighting device, it is necessary to eliminate these drawbacks. The lens film (B) of the present invention has these defects suppressed as compared with the prism lens film, but is not sufficient to meet the market demand. The light diffusion laminate of the present invention solves this by the lamination of the second light diffusion member (C).

  In order to make the surface glossiness in the above range, the total light transmittance / parallel light transmittance ratio measured by the method described in the embodiment of the second light diffusing member (C) is 1.0 to as described later. An appropriate range of 30 is necessary. Thereby, the appearance defect can be improved in a form in which the above-described deterioration of the effect of the present invention is suppressed.

(Structure of the first light diffusion member (A))
The first light diffusing member (A) used in the light diffusing laminate of the present invention includes at least one layer composed of a mixture of at least two resins that are incompatible with each other, and has a total light transmittance / parallel light transmittance ratio. If it is 8-110, it will not be limited.
The 1st light-diffusion member (A) in this invention points out the internal light-diffusion type optical member which expresses light diffusivity by including the light-diffusion layer which consists of a light-diffusion component which consists of the above-mentioned incompatible mixture. As described later, the first light diffusion member (A) includes a configuration in which the light diffusion layer is a surface layer and a configuration in which the light diffusion layer is an inner layer.
When a layer made of a mixture of at least two kinds of resins that are incompatible with each other is present in the light diffusing member, light is scattered by the difference in refractive index at the interface between the respective resins when the light passes through the layer. Then, the light diffusivity of this layer varies depending on the refractive index difference of each resin, the ratio of each resin and the layer thickness. Also, one resin often exists in the form of particles depending on the ratio of each resin. The particles constitute a light diffusing component, and the light diffusivity varies depending on the size of the light diffusing component. In order for the above-described total light transmittance / parallel light transmittance ratio to be in the above range, it is preferable to appropriately adjust these constituent requirements.
For example, the refractive index difference is preferably in the range of 0.003 to 0.07, more preferably in the range of 0.005 to 0.06, and still more preferably 0.01 to 0.05. Moreover, 5 micrometers-10 mm are preferable, as for the thickness of a layer, 10 micrometers-5 mm are more preferable, and 20 micrometers-4 mm are still more preferable. Moreover, it is preferable to set suitably the ratio of each resin with the combination of the said component.

  The size of the light diffusion component is affected by many factors such as the type and ratio of the resin and the film forming conditions. The total light transmittance / parallel light transmittance ratio described above is the number of times that light is scattered by a light diffusion component when light passes through a layer made of a mixture of at least two kinds of resins that are incompatible with each other. The average diameter in the thickness direction of the layer of the light diffusing component is important because it is presumed to be greatly affected by the number of times. The thickness is preferably at least ½ or less of the thickness of the film. 1/3 or less is more preferable, and 1/10 or less is more preferable. Moreover, when the cross section of a film is observed with an electron microscope, it is preferable that the number of light diffusing component particles existing in a linear shape is 5 or more when an arbitrary straight line is drawn in the thickness direction. 10 or more are more preferable, and 30 or more are more preferable. In order to make the constituent factors within a preferable range, it is preferable to optimize requirements such as layer thickness, resin type and blending ratio, and film forming conditions. For example, the preferred embodiments described below are important factors.

  In the first light diffusing member (A), since the uniformity of the in-plane optical characteristics is important, it is preferable that the light diffusing component exists as uniformly as possible in the surface. However, the uniformity of the light diffusion component in the thickness direction is not limited as long as the uniformity of the in-plane optical characteristics is ensured. For example, the light diffusing component may exist locally in a specific portion in the thickness direction.

As the resin constituting the mixture of at least two kinds of resins that are not compatible with each other, so-called resin beads, which are non-melting fine particle resins, may be used. However, when the resin beads are used, the filtration in the film forming process may cause clogging of the filtration filter, which may cause a problem in productivity. Moreover, since the clarity of the obtained optical member may be inferior, it is preferable that all types of resins are made of a mixture of thermoplastic resins and formed by a melt extrusion molding method.
Furthermore, in the said aspect, it is more preferable that the quantity of the thermoplastic resin component which comprises the island structure in the mixture of an at least 2 sort (s) of thermoplastic resin is 11-50 mass% with respect to the total amount of thermoplastic resins.

  Further, the first light diffusion member (A) in the present invention may have a single layer configuration or a multilayer configuration of two or more layers. In the case of a multilayer structure, at least one layer may be composed of a blend of at least two resins that are not compatible with each other. For example, a single layer structure consisting of only a light diffusion layer, a light diffusion layer / light diffusion layer, a light diffusion layer / a non-light diffusion layer (for example, a simple transparent layer) / a light diffusion layer, a non-light diffusion layer / a light diffusion layer / Non-light diffusion layer, light diffusion layer / light diffusion layer, light diffusion layer / light diffusion layer / non-light diffusion layer, light diffusion layer / light diffusion layer / non-light diffusion layer, and light diffusion layer / non-light diffusion layer / light A multilayer structure such as a diffusion layer may be mentioned. Furthermore, the structure which increased the number of layers from these may be sufficient. In the case of the multilayer structure, it may be produced by a multilayer coextrusion method, or may be carried out by an extrusion lamination method or a dry lamination method.

(Mixture of at least two mutually incompatible thermoplastic resins)
In the present invention, examples of the thermoplastic resin used in the mixture of at least two incompatible thermoplastic resins include polyethylene resins, polypropylene resins, polybutene resins, cyclic polyolefin resins, and polymethylpentene resins. Polyolefin resins, polyester resins, acrylic resins, polystyrene resins, polycarbonate resins, fluorine resins, and copolymers thereof. From these thermoplastic resins, at least two types of incompatible (incompatible with each other) thermoplastic resins may be selected, but at least one of the above properties can be expressed stably and economically. The seed is preferably made of a polyolefin resin.

  The other resin of the two types of resins is preferably a polyolefin resin, a polyester resin, a fluorine resin, or the like, and is appropriately selected in consideration of required characteristics other than optical characteristics, economy, and the like.

  In particular, from the viewpoint of light resistance and economy, it is preferable to use polyolefin resins for both types. The refractive index difference between the two types of resins is not limited, but the refractive index difference is preferably in the range of 0.003 to 0.07. The range of 0.05-0.005 is more preferable, and 0.01-0.02 is further more preferable.

  For example, in the case of the sea / island method, the melt flow rate of the thermoplastic resin used as the at least two incompatible thermoplastic resins largely changes depending on the combination of the respective melt flow rates, and the optical characteristics change. Therefore, it may be appropriately selected according to the required optical characteristics and the size and shape of the island phase. For example, when the polyolefin resin is used for both of the above two types, the melt flow rate measured at 230 ° C. may be appropriately combined within the range of 0.1 to 100.

  In the present invention, it may be preferable to impart anisotropy to the light diffusion degree. In order to impart this characteristic, it is preferable to give anisotropy to the island structure. In order to form an island structure having such a shape, it is preferable to make a difference in melt viscosity between the sea component resin and the island component resin. In particular, it is preferable to lower the melt viscosity of the island component than the sea component. For this purpose, for example, it is preferable to provide a difference in melt flow rate, and it is preferable to increase the melt flow rate of the island component rather than the sea component. It is also preferable to make a difference between the rigidity of the sea component resin and the island component resin. In particular, it is preferable to lower the rigidity of the island component than the sea component.

  In addition, when the melt flow rate of the island component is low, it is difficult to apply a force for thinning the island component due to the share or draft in the die, and the anisotropy may decrease. This tendency becomes stronger as the mass ratio goes away from 50/50. Each characteristic is adjusted in consideration of these tendencies.

  The type of the two resins is not limited as long as the refractive index difference is satisfied. For example, a combination of a cyclic polyolefin-based resin and a polyethylene-based resin can easily obtain the optical characteristics of the present invention and is economical. Since it is excellent, it is preferable. In addition, there is a feature that it is excellent in UV resistance.

  Examples of the cyclic polyolefin-based resin include those having a cyclic polyolefin structure such as norbornene and tetracyclododecene. Specifically, for example, (1) a resin obtained by subjecting a ring-opening (co) polymer of a norbornene-based monomer to polymer modification such as maleic acid addition or cyclopentadiene addition as necessary, followed by hydrogenation (2) Resin obtained by addition polymerization of norbornene monomer, (3) Resin obtained by addition copolymerization of norbornene monomer and olefin monomer such as ethylene and α-olefin. . The polymerization method and the hydrogenation method can be performed by conventional methods.

  The polyethylene resin may be a single polymer or a copolymer. In the case of a copolymer, it is preferable that 50 mol% or more is an ethylene component. The density and polymerization method of the resin are not limited, but it is preferable to use a copolymer having a density of 0.909 or less. Examples thereof include copolymers with propylene, butene, hexene, octene and the like. The polymerization method may be either a metallocene catalyst method or a nonmetallocene catalyst method. In particular, it is preferable to use a block copolymer of ethylene and octene in that high diffusibility can be stably imparted. Examples of the resin include INFUSE (TM) manufactured by Dow Chemical Company. The reason why it is preferable to use the block copolymer of ethylene and octene is not clear, but it is presumed that the compatibility with the cyclic polyolefin resin is superior to other polyolefin resins.

  In the case of a combination of a cyclic polyolefin resin and a polyethylene resin, the polyethylene resin in the sea phase is used as the sea phase, and the melt flow rate of the polyethylene resin in the sea phase is higher than the melt flow rate of the cyclic polyolefin resin in the island phase. It is preferable to do.

  In the case of a combination of a cyclic polyolefin resin and a polyethylene resin, it is preferable that 10 to 60% by mass of the cyclic polyolefin resin is blended in the total resin amount, and more preferably 10 to 50% by mass.

  The resin may be selected from commercially available resins with high versatility. However, a custom-made product may be used for measures such as more stable production.

  The portions detailed above are merely examples, and the present invention is not limited to these. What is necessary is just to select suitably in the range with which the said optical characteristic is satisfy | filled.

(Method for producing first light diffusing member (A))
Although the manufacturing method of the 1st light-diffusion member (A) of this invention is not specifically limited, From the point of economical efficiency, the method of forming into a film by melt extrusion molding is preferable. The film forming method is not particularly limited, and for example, either the T-die method or the inflation method may be used. Moreover, the film may be an unstretched film or may be subjected to a stretching process. In the case of a structure including two or more layers, it is preferable to form a film by a coextrusion method, but there is no limitation. For example, it may be manufactured by an extrusion lamination method, or two or more films may be bonded together with an adhesive or the like.

The first light diffusion member (A) is preferably highly isotropic, but is not limited. In order to approach the isotropic property, the following method is preferable.
It is preferable to form a film by extruding a resin melted by an extruder in a sheet form from a die, and press-contacting the sheet to a cooling roll with a pressure roll to allow it to cool and solidify. The specific content is not limited as long as it satisfies the condition of being brought into close contact with the cooling roll by the pressure roll. For example, it may be pressed with a pressing roller having a smaller diameter than a cooling roll that is generally implemented, or a sheet is extruded between two cooling rolls having the same diameter and pressed between the cooling rolls. Also good. Moreover, in this method, you may perform the roughening by the above-mentioned shaping process simultaneously using the roll which roughened the surface of this pressing roll and / or cooling roll.

  In the case of obtaining isotropic properties, it is preferably produced without stretching and without being drafted during melt extrusion, but it is also possible to use a plurality of anisotropic films as described below. That is, a polyester resin is used for the internal light diffusion layer, and the island phase is stretched in the stretching direction by stretching 2 to 10 times in one direction to form an elongated structure. Light diffusion in a direction perpendicular to the orientation direction of the island phase And the high light diffusibility aimed by the present invention can be secured. It is preferable to use two or more films so that the main light diffusion directions are perpendicular to each other.

  The mixture of the at least two incompatible thermoplastic resins may be blended with each of the thermoplastic resins by an extruder in the film forming process, or in a form that has been previously mixed by a kneading method or the like. It may be used.

(Control method of the total light transmittance / parallel light transmittance ratio of the first light diffusing member (A))
The method for controlling the total light transmittance / parallel light transmittance ratio to the above-described preferable range is not limited, and the type of resin, the composition ratio, and the manufacturing conditions as described above may be appropriately optimized. In the case of the light diffusing member (A), the total light transmittance / parallel light transmittance ratio is greatly influenced by the thickness of the light diffusing layer, and is preferably controlled by the thickness of the light diffusing layer.

(Characteristics of second light diffusion member (C))
The second light diffusing member (C) of the present invention needs to have a total light transmittance / parallel light transmittance ratio of 1.0 to 30 as measured by the method described in Examples. 1.1-25 are more preferable and 1.2-23 are especially preferable. When the total light transmittance / parallel light transmittance ratio is less than 1.0, the above-described surface glossiness is increased, and the appearance defect is deteriorated. On the contrary, when the total light transmittance / parallel light transmittance ratio exceeds 30, the front luminance is lowered, which is not preferable.

(Structure and manufacturing method of second light diffusion member (C))
As long as the second light diffusing member (C) satisfies the above characteristics, its configuration, manufacturing method, and the like are not limited. For example, an internal light diffusion type such as the first light diffusion member (A) described above or a surface light diffusion type may be used.

  In the case of the internal light diffusion type, a material satisfying the above total light transmittance / parallel light transmittance ratio characteristics can be selected from those obtained by the same configuration and manufacturing method as the first light diffusion member (A) described above. good.

On the other hand, in the case of the surface light diffusion type, a material satisfying the above-mentioned total light transmittance / parallel light transmittance ratio characteristics may be selected from those obtained by the following configuration and manufacturing method. In the case of the surface light diffusion type, light is scattered on the surface by laminating a layer containing fine particles on the surface of the base material or by forming surface irregularities by shaping the surface of the base material.
Below, taking a film as an example, a surface light diffusion type by laminating layers containing fine particles and a surface light diffusion type by surface unevenness by shaping will be described. A sheet or plate may be used as the substrate.

As the former type (surface light diffusion type by laminating layers containing fine particles), for example, a structure in which a light diffusion layer composed of a layer containing fine particles is laminated on a transparent base film is preferable.
Transparent base films include, for example, polyester resins, acrylic resins, acrylic urethane resins, polyester acrylate resins, polyurethane acrylate resins, epoxy acrylate resins, urethane resins, epoxy resins, polycarbonate resins, and cellulose resins. Resin, acetal resin, vinyl resin, polyethylene resin, polystyrene resin, polypropylene resin, polyamide resin, polyimide resin, melamine resin, phenol resin, silicone resin, fluorine resin, polypropylene resin and cyclic resin A transparent plastic film in which one or more of polyolefin-based resins such as olefin resin are mixed can be used. Of these, a stretched polyethylene terephthalate film, particularly a biaxially stretched film, is preferred because of its excellent mechanical strength and dimensional stability. Moreover, in order to improve adhesiveness with a light-diffusion layer, what gave the surface a corona discharge process or provided the easily bonding layer is used suitably. In addition, it is preferable that the thickness of a base film is about 0.1-5 mm normally.

  The light diffusing layer is preferably formed mainly by laminating a layer in which particles forming a surface uneven shape are blended with a polymer resin. As the polymer resin, a resin excellent in optical transparency can be used. For example, a polyester resin, an acrylic resin, an acrylic urethane resin, a polyester acrylate resin, a polyurethane acrylate resin, an epoxy acrylate resin, Heat of urethane resin, epoxy resin, polycarbonate resin, cellulose resin, acetal resin, polyolefin resin, polystyrene resin, polyamide resin, polyimide resin, melamine resin, phenol resin, silicone resin, etc. A plastic resin, a thermosetting resin, an ionizing radiation curable resin, or the like can be used. Among these, acrylic resins having excellent light resistance and optical properties are preferably used.

  In addition to inorganic fine particles such as silica, clay, talc, calcium carbonate, calcium sulfate, barium sulfate, aluminum silicate, titanium oxide, synthetic zeolite, alumina, smectite, styrene resin, urethane resin, etc. Organic fine particles made of benzoguanamine resin, silicone resin, acrylic resin, or the like can be used. Among these, it is preferable to use organic fine particles from the viewpoint of easily obtaining spherical particles and easily controlling to a desired uneven shape. The particles can be used in combination of not only one type but also a plurality of types.

  In the case of using a resin, for example, a bead-like particle such as a polymer bead may be used, or a mixture of resins that are incompatible with each other is used to form a particle, so-called sea / island method or the like. Also good.

  The content ratio of the particle component with respect to the polymer resin cannot be generally specified depending on the average particle diameter of the particles used and the thickness of the light diffusion layer, but is preferably 70 to 220 parts by weight with respect to 100 parts by weight of the polymer resin. More preferably, it is 120 to 220 parts by weight.

  Although the shape of particle | grains is not specifically limited, From a viewpoint of making the uneven | corrugated shape of this invention easy to obtain, it is preferable that it is a spherical particle. Moreover, it is preferable to set it as 1-30 micrometers from the same viewpoint as average particle diameter of particle | grains.

  In the concavo-convex layer, in addition to the above-mentioned polymer resin and particles forming the concavo-convex shape, surfactants such as photopolymerization initiators, photopolymerization accelerators, leveling agents and antifoaming agents, antioxidants, ultraviolet absorbers You may add additives, such as these, resin and particle | grains other than having mentioned above. These may be selected from commercially available products or may be newly developed. What is necessary is just to select suitably by cost performance.

  The manufacturing method of the surface light-diffusion member containing the light-diffusion layer which consists of a layer containing said fine particle is also not limited. For example, a coating solution for a light diffusing layer in which a material such as the binder resin and particles described above is dissolved in a suitable solvent, a conventionally known method such as a bar coater, a blade coater, a spin coater, a roll coater, a gravure coater, It can be produced by applying onto a support by a flow coater, die coater, spray, screen printing or the like and drying. Moreover, you may manufacture by the method of mix | blending particle | grains with the surface layer as a multilayer structure by a coextrusion method. The light diffusion layer may be formed on one side or may be formed on both sides.

  The latter type (surface light diffusion type due to surface irregularities by shaping) can be formed by a transfer shaping technique such as an embossing method. For example, the method similar to the manufacturing method of the lens film (B) mentioned above is mentioned.

(Configuration of light diffusion laminate)
The configuration of the light diffusion laminate of the present invention requires that the first light diffusion member (A), the lens film (B), and the second light diffusion member (C) are laminated in this order. When the stacking order is changed, the effect of the present invention is not naturally exhibited.
In the above configuration, the lens film (B) needs to be laminated so that the lens surface is in contact with the second light diffusion member (C). Laminating in the reverse direction improves the appearance defect even without the second diffusion film (C), but is not preferable because the condensing effect of the lens film is greatly reduced and the front illuminance and front brightness are reduced.
Further, in the above configuration, an air layer is present at the interface between the first light diffusion member (A) and the lens film (B) and / or the interface between the lens film (B) and the second light diffusion member (C). It is preferable to do. In order for an air layer to exist at the interface, the first light diffusing member (A) or the second light diffusing member (C) and the lens film (B) may be simply overlapped and laminated. Moreover, in order to prevent the shift | offset | difference at the time of use with a 1st light-diffusion member (A) or a 2nd light-diffusion member (C), and a lens film (B), the corner part of a laminated body, the edge part, etc. are made into parts. For example, or may be partially bonded to the entire surface of the laminate using, for example, an adhesive dispersed in a dot shape. On the other hand, if the entire surface is bonded with an adhesive or a pressure-sensitive adhesive, the air layer at the interface is eliminated, and the condensing effect by the lens film (B) is lowered, and the front luminance and the front illuminance improvement effect may be reduced. There is.

(Action mechanism)
The present invention breaks the relationship between front luminance and front illuminance and luminance spots, which are said to be a contradictory phenomenon, by a new concept, and aims to achieve both high front luminance and front luminance and low luminance spots. In other words, in the prior art, the use of a light diffusing plate with a high light diffusivity or the combination of a plurality of light diffusing members has been used to suppress brightness spots, so lowering the brightness spots reduces the front brightness and front illuminance, The so-called contradictory event was not completely overcome.

  The inventors of the present invention, as the first light diffusing member (A), have a low light diffusivity and a small effect of reducing luminance spots, but if the luminance spots are reduced by a synergistic effect in combination with the lens film (B). It was thought that brightness spots can be reduced in a form that suppresses the decrease in front brightness and front brightness, and that both high front brightness and front brightness and low brightness spots, which could not be realized by the prior art, can be achieved. That is, the light diffusivity of the first light diffusing member (A) is in an appropriate range, and the light diffusivity necessary for reducing the luminance spots is achieved by utilizing a synergistic effect with the lens film (B). I hypothesized that it was preferable.

  As a result of intensive studies, the relationship between front luminance and front illuminance and luminance unevenness is not a contradiction with respect to the light diffusivity of the first light diffusing member, but has a maximum value and a minimum value, respectively. Since the light diffusivity of the first light diffusing member (A) showing the values is almost the same, by selecting an appropriate range centered on this point, the high front luminance and front illuminance that could not be achieved by the prior art are low. It has been found that both brightness spots can be achieved.

  The correctness of the above hypothesis was verified because the total light transmittance that can eliminate the influence of the pattern of the angle distribution pattern of the outgoing light, which was a problem in the above-described conventional light diffusion degree evaluation / This was achieved for the first time by establishing a novel light diffusivity evaluation method called parallel light transmittance ratio.

  As described above, in the present invention, the synergistic effect of the light diffusivities of the first light diffusing member (A) and the lens film (B) is used to achieve both high front luminance and front luminance and low luminance spots. The light diffusion degree of the light diffusion laminate is also important. For example, the total light transmittance / parallel light transmittance ratio of the light diffusing member 1 and the lens film 1 used in Example 1 is 46 and 46, respectively, and the light diffusivity is medium. On the other hand, the total light transmittance / parallel light transmittance ratio of the laminate of the light diffusing member 1 and the lens film 1 is 81.5, and the light diffusivity increases due to the synergistic effect of both members. The validity of the above hypothesis is shown.

  In a system in which the lens film (B) is limited to the lens film 1 and various light diffusing members having different total light transmittance / parallel light transmittance ratios are combined, the total light transmittance / parallel light transmission of the light diffusion laminate. A suitable range for the ratio is 80-120. However, it was found that the appropriate range is affected by the lens structure of the lens film (B). Accordingly, it is necessary to establish a universal evaluation scale for the light diffusion degree of the first light diffusion member (A) that is not affected by the lens structure of the lens film (B).

  The inventors of the present invention are affected by the lens structure in the total light transmittance / parallel light transmittance ratio. The light diffusion degree of the light diffusion laminate does not act as a primary function of the contribution of diffuse transmission light. We inferred that this was a result of acting as a next function. Therefore, the verification was performed considering that a composite characteristic obtained by multiplying the total light transmittance / parallel light transmittance ratio by the total light transmittance including the contribution of diffuse transmitted light is effective. As a result, the expected result was obtained. The inventors have found that the above-described range of 2500 to 4000 is appropriate for achieving both high front luminance and front luminance and low luminance spots.

  The composite characteristic is a value obtained by dividing the square of the total light transmittance including the contribution of diffuse transmitted light by the parallel light transmittance, and is therefore a measure by which the contribution of diffuse transmitted light acts in a multi-order function. We believe that we support the above hypothesis. Therefore, hereinafter, this scale is sometimes referred to as a secondary function light diffusivity.

  Note that the total light transmittance / parallel light transmittance ratio, which is the primary function light diffusivity, is sufficient for the light diffusivity of the first light diffusing member (A), and it is not necessary to use the secondary function light diffusivity. In the case of the light diffusing laminate, the secondary function light diffusivity is preferable. In the case of the light diffusing laminate, the light diffusivity is governed by the synergistic effect of the first light diffusing member (A) and the lens film (B). Is presumed to be caused by this.

  In other words, luminance spots are a phenomenon in which bright areas and dark areas are visually recognized when surface illumination is observed from a certain angle. In order to suppress such luminance unevenness, a light diffusing member having a high light diffusivity is usually used. The premise that luminance spots can be suppressed by such means is that there is no significant difference in the amount of light emitted from a bright-looking region and a dark-looking region. That is, a region with a large amount of light emitted in the angle direction for observing the surface illumination is observed brightly, whereas a region that appears dark has a relatively small amount of light emitted in the angle direction for observing the surface illumination. On the other hand, this relationship is reversed for the amount of light emitted outside the angle. That is, a light diffusion plate or light diffusion sheet having a high light diffusion degree reduces the light emitted by diffusing the light emitted in the observation direction of the brightly visible region, while the light emitted in the direction other than the observation direction of the darkly visible region. By diffusing, a part of the emission direction is changed to the observation direction, and the amount of light in the observation direction is increased. As a result, luminance unevenness is suppressed. Here, in general, the observation direction is often the normal (front) direction of surface illumination.

  The lens structure on the surface of the lens film (B) of the present invention is preferably composed of two lens arrays whose extending directions are substantially orthogonal. Thereby, since the visual field in two directions can be controlled symmetrically, the visual field in the 360 degree direction can be controlled as a result. Further, such a lens structure has a feature that reflects light incident along the normal direction and emits light incident at an oblique angle other than the normal direction by deflecting it in the normal direction by refraction. . In other words, the light diffusion member having a high light diffusion degree as described above can obtain the same action in the 360 degree direction as the action of suppressing luminance unevenness.

  In order to suppress the luminance unevenness of the surface illumination by the lens structure, it is important to balance the light amount incident on the lens film (B) between the light amount in the normal direction and the light amount other than the normal direction. As a result of intensive studies by the inventors, the first light diffusing member (A) having the light diffusing performance as described above is inserted between the surface light source, thereby suppressing luminance unevenness and high luminance. Both are possible.

  On the other hand, the extraction efficiency of light emitted from the light source of the backlight device by the lens film (B) is governed by the surface area of the surface of the lens film (B), and the higher the surface area, the higher the extraction efficiency. Brightness is obtained. Therefore, it is preferable to increase the center plane particle size (SGr) having a correlation with the surface area of the lens surface of the lens film (B). It is clearly shown in FIG. 8 that the center plane particle size (SGr) of the lens surface of the lens film has an influence on the front luminance and luminance unevenness.

  Furthermore, the isotropic distribution distribution profile of the emitted light of the lens film (B) is high, and there is no drop in the emitted light intensity near the emission angle of 45 degrees of the emitted light distribution profile. These disadvantages of the prism lens film are improved by use, and it is possible to achieve both high front luminance and low luminance spots. This reason is caused by the fact that the degree of synergistic effect on the light diffusion degree by the combination of the first light diffusion member (A) and the lens film (B), which is the basis of the present invention, varies slightly depending on the lens structure. Because it is. To improve the above characteristics, the above-described measures are preferable.

  The reason why the appearance defect is improved by laminating the second light diffusing member (C) on the lens surface of the lens film (B) is that the emitted light emitted from the lens film (B) is emitted from the second light diffusing member (C). This is because the intensity of light in the direction causing the appearance defect is suppressed by being scattered and diffused when passing through (). However, this effect is a contradictory phenomenon between the front luminance and the front illuminance. Similar to the compatibility of frontal luminance, frontal illuminance, and luminance unevenness, the total light transmittance that can eliminate the influence of the pattern of the variable-angle light distribution profile of the emitted light, which has been a problem of the conventional light diffusion degree evaluation / This was achieved for the first time by establishing a novel light diffusivity evaluation method called parallel light transmittance ratio.

(Surface light source device)
The basic unit of the surface light source device of the present invention is not particularly limited as long as it has a light exit surface on at least one surface. For example, any of an edge light system and a direct type may be used. Moreover, a double-sided light emission type may be used. A direct type is preferred. The light diffusion laminate of the present invention is used on at least one surface of a surface light source device.

  Generally, in the surface light source device, a reflective film or a reflector is used on the surface opposite to the light exit surface for the purpose of increasing the brightness of the light exit surface. The type of the reflective film or reflector is not limited. For example, a light diffusion type reflection film or reflector made of a white body, a highly directional reflection film or reflector utilizing reflection by metallic luster, and a reflection film or reflector having both characteristics can be mentioned. it can.

  In addition, edge light type surface light source devices employ a method of attaching a light emission pattern by printing, engraving, engraving, or the like in order to suppress luminance attenuation due to the distance from the light source. It doesn't matter. The method of providing the light emission pattern differs from the method of the present invention in that the light emission profile is significantly different from the method of simply superimposing various optical members implemented in the prior art. It is preferably designed to be compatible with the inventive method. In the method of the present invention, the amount of emitted light at a shorter distance than that of the light source increases, so that it is preferable to make the inclination of the light emission pattern stronger.

(Light source of surface light source device)
The light source used for the surface light source device of the present invention is not limited. For example, light sources such as fluorescent lamps, cold cathode fluorescent lamps, and LED light sources that are already widely used. In particular, the light diffusing laminate of the present invention is excellent in concealing hot spots of the light source, so that the lamp image of the LED light source with high straightness of light, the so-called light source spot is suppressed in the form of suppressing the decrease in luminance and illuminance. The use of an LED light source is preferred because it can be erased.

(Usage method of light diffusion laminate)
The light diffusion laminate of the present invention needs to be installed so that the first light diffusion member (A) surface of the light diffusion laminate is in contact with the light exit surface side surface of the surface light source device. By doing in this way, the effect of the present invention can be expressed effectively. When the second light diffusing member (C) is installed in the reverse direction so that the surface of the second light diffusing member (C) is in contact with the exit surface side of the surface light source device, the front illuminance and the front luminance may be significantly reduced, and the luminance unevenness may increase. Therefore, it is not preferable. Moreover, it is preferable that the light-emitting surface side surface of the surface light source device and the first light diffusion member (A) surface of the light diffusion laminate are bonded together with a transparent adhesive or pressure-sensitive adhesive. By doing in this way, the condensing effect by a lens film (B) increases, and front brightness can be raised.
If it is said installation method, the installation direction of a 1st light-diffusion member (A) will not ask | require. The light diffusion layer surface may be in a direction in contact with the lens film (B), or the light diffusion layer surface may be in a direction in contact with the surface light source device. When the surface light diffusion type is used as the second light diffusion member (C), it is preferable that the second light diffusion member (C) is installed so that the opposite surface of the light diffusion layer is in contact with the lens film (B).

(Luminance or illuminance characteristics of surface light source device)
In the surface light source device of the present invention, it is preferable that the isotropy of the luminance distribution profile and the numerical value of the rank of the luminance drop at the intermediate angle of the luminance distribution profile are as small as possible. By doing in this way, when the surface light source device of the present invention is used for general illumination, uniform illumination without directionality can be achieved.

(Lighting device)
In this invention, the said surface light source device can be used as a light source of an illuminating device. Since the surface light source device can reduce high luminance, that is, high illuminance and unevenness of illuminance, when used as a light source for illumination, the brightness and uniformity of the illumination device can be improved. Alternatively, in usage methods that do not require a high level of illuminance, the light quantity of the lamp can be reduced, so that the manufacturing cost of the lighting device and the energy consumption during use of the lighting device can be reduced. It becomes possible to reduce. Although the kind of illuminating device is not limited, It is especially preferable to use it for flat type illuminations, such as a room and a vehicle.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, and is implemented with appropriate modifications within a range that can be adapted to the gist of the present invention. These are all included in the technical scope of the present invention.

  The measurement / evaluation methods employed in the examples are as follows. In the examples, “parts” means “parts by mass” unless otherwise specified, and “%” means “% by mass” unless otherwise specified.

1. Total light transmittance / parallel light transmittance ratio and combined characteristics of total light transmittance / parallel light transmittance ratio and total light transmittance (second-order function light diffusivity)

(Total light transmittance)
An integrating sphere attachment device (ISR-3100: manufactured by Shimadzu Corporation) is set in a self-recording spectrophotometer (UV-3150: manufactured by Shimadzu Corporation), and a range of 300 to 800 nm in wavelength with a slit width of 12 nm is scanned at high speed. The spectrum was measured and displayed as a transmittance at 550 nm.

(Parallel light transmittance)
Using a self-recording spectrophotometer (UV-3150; manufactured by Shimadzu Corporation), a spectrum range was measured by scanning a wavelength range of 300 to 800 nm at a slit width of 12 nm at a high speed, and the transmittance was displayed at 550 nm.
In the above measurement, the value when measured by fixing to the sample fixing device so that the main light diffusion direction of the sample is horizontal is used for both the light diffusion member and the light diffusion laminate.
The main light diffusion direction was detected by the following method.
In the case of the light diffusing member, light was applied to the sample with a laser marker, and the light diffusion direction of the emitted light was detected and determined. In the case of a lens film, the lens film and the light diffusion film (Kimoto light up film (TM) 100DX2) are overlapped so that the opposite surface of the lens surface of the lens film and the light diffusion layer side of the light diffusion member are in contact with each other, The pattern of the emitted light of the laser marker was projected on a white plate at a distance of about 3 cm in the dark by applying light with a laser marker from the light diffusing member side, and the determination was made based on the pattern.
In the light diffusing member, when the surface roughness is different between both surfaces of the sample, it is preferable to measure by fixing the sample in the direction in which the light transmission direction in actual use matches. In the present invention, the measurement was carried out with the surface being fixed in the direction in which light enters from the lower surface roughness.
In the case of a lens film, light was incident from the opposite side of the lens surface and measured.
In the case of the light diffusing laminate in which the light diffusing member and the lens film are laminated, the measurement was performed by fixing the opposite surface of the lens film and the light diffusing member and fixing the light diffusing member to the sample fixing device in the direction of entering from the light diffusing member side.
In the light diffusing member, when the surface roughness is different between both surfaces of the sample, it is preferable to measure by fixing the sample in the direction in which the light transmission direction in actual use matches. In the present invention, the measurement was carried out with the surface being fixed in the direction in which light enters from the lower surface roughness.

(Total light transmittance / parallel light transmittance ratio)
The total light transmittance measured by the above method was calculated by dividing by the parallel light transmittance. The higher the value of the total light transmittance / parallel light transmittance ratio, the higher the light diffusivity.

(Secondary function light diffusivity)
The total light transmittance / parallel light transmittance ratio determined by the above method was multiplied by the total light transmittance.

2. Non-spectral total light transmittance and haze Measured in accordance with JIS K 7136 using a Nippon Denshoku Industries Co., Ltd. haze measuring instrument “NDH-2000”.
In the above measurement, the value when measured by fixing to the sample fixing device so that the main light diffusion direction of the sample is horizontal was used. The main light diffusion direction was determined by applying light to the sample with a laser marker and detecting the light diffusion direction of the emitted light.
When the surface roughness differs between the two surfaces of the sample, it is better to measure by fixing the sample in the direction in which the light transmission direction in actual use matches. In the present invention, the measurement was carried out with the surface being fixed in the direction in which light enters from the lower surface roughness.

3. Diffuse light transmittance This was measured according to JIS K 7361 using a haze / transmittance meter “HR-100” manufactured by Murakami Color Research Co., Ltd.
In the above measurement, the value when measured by fixing to the sample fixing device so that the main light diffusion direction of the sample is horizontal was used. The main light diffusion direction was determined by applying light to the sample with a laser marker and detecting the light diffusion direction of the emitted light.
When the surface roughness differs between the two surfaces of the sample, it is better to measure by fixing the sample in the direction in which the light transmission direction in actual use matches. In the present invention, the measurement was carried out with the surface being fixed in the direction in which light enters from the lower surface roughness.

4. Center plane grain size (SGr)
It measured and calculated | required on the conditions shown below with the contact-type three-dimensional surface roughness measuring apparatus (Kosaka Laboratory Co., Ltd. two-dimensional, three-dimensional surface roughness analysis system TDA-21).
(Measurement condition)
TABLE PITCH: 0.005,
REC PITCH: 1,
H. MAGNIFICATION: 200,
MEASURING LENGTH: 1mm,
V. MAGNIFICATION: 500,
CUT OFF: 0.25,
TRAVERSING LENGTH: REC,
Number: 100 The stylus was 2 μm and 90 degrees.

5. Isotropic lens film and drop in emitted light intensity at an output angle of 45 degrees (1) Lens film isotropy Variable angle spectrophotometric system GCMS-4 type (GSP-2 type: manufactured by Murakami Color Research Co., Ltd.) The measurement was performed using a variable angle spectrophotometer GPS-2 type). Transmission measurement mode, light incident angle: 0 ° (film normal direction), light receiving angle: −80 ° to 80 ° (polar angle from film normal, azimuth angle is horizontal), light source: D65, field of view: 2 ° The sample is fixed to the sample stage so that the main light diffusion direction of the sample is horizontal and vertical (the deviation between the axis of the sample table and the axis of the main light diffusion direction is allowed up to about 20 degrees), A variable-angle luminous intensity curve was obtained from the Y value of the Lab chromaticity data of the transmitted light. The tilt angle was 0 °. The angle was measured by changing the angle at a pitch of 5 °.
Prior to the measurement, the apparatus was calibrated using a transmission diffusion standard plate (opal glass) for GCMS-4 manufactured by Murakami Color Research Co., Ltd., and the transmitted light intensity at the light receiving angle of 0 degree of the transmitted light diffusion standard plate was measured. Relative transmittance was measured as a reference (1.000). The transmitted light diffusion standard plate had a transmittance at 440 nm of 0.3069 when the air layer was 1.000 by integrating sphere spectroscopic measurement.
In the measurement, the standard light diffusing plate and the surface opposite to the lens surface of the lens film were overlapped and fixed to the sample stage so that the standard light diffusing plate side was the light incident side.
The half-value width angle (angle of the change-angle light intensity curve at half the Y value of 0 degree) was determined from the variable-angle light intensity curve in both directions, and the smaller half-value width was obtained as the greater half-value width value. . A direction closer to 1 is more isotropic.
The measurement with the standard light diffusing plate is performed because when the lens film alone is measured, the variable light intensity curve becomes complicated and it is difficult to obtain the half width.

(2) Decrease in emitted light intensity at an exit angle of 45 degrees of the lens film The following formula was calculated from the Y values of the exit angles of 45 degrees and 70 degrees measured by the above method.
It calculated | required about the said both directions and the value with the smaller value was used.
Depth of emitted light intensity at 45 degree exit angle of lens film = Y value of 45 degrees / Y value of 70 degrees

6. Surface glossiness In the case of the lens film (B) alone, the surface glossiness of the lens surface, and in the case of the laminated body of the lens film (B) and the second light diffusion member (C), the upper light diffusion member (C ) The surface glossiness of the lens surface was measured using a gloss meter “VG2000” manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS Z 8741 at a 60 ° angle. In the measurement, values in both the main light distribution direction and the direction orthogonal to the main light distribution direction were measured, and the value having the higher glossiness was defined as the surface glossiness.

7. Brightness and luminance spots in a cold cathode tube type direct surface light source device were measured using RISA-COLOR / ONE-II (manufactured by Highland).
Remove the milk light diffuser of the cold cathode tube type light source device for inspection (light emitting part number LB350-236 and power supply part number SWD24-3.2A) manufactured by Dentsu Sangyo Co., Ltd. An acrylic plate having a transparent thickness of 2 mm was placed, and an A-4 size sample was placed on the transparent acrylic plate so as to be approximately in the center of the surface light source device for inspection. Further, a black light-shielding plate provided with a 100 mm square opening was placed on this material so that the opening was approximately the center of the sample, and the measurement was performed.
The lens film was installed in a direction in which the main orientation direction of the lens film was parallel to the longitudinal direction of the surface light source device.
The main orientation direction of the lens film is such that the light diffusion layer side of the light-up film 100DX2, which is a light film manufactured by Kimoto, is in contact with the anti-lens surface of the lens film, and the light of the laser marker is applied from the light-up film side. Determination can be made by projecting the pattern of the emitted light onto the walls separated by about 2 cm. The longitudinal direction of the projection light pattern is the main light diffusion direction. The determination was performed in the dark.
When the light diffusing member has anisotropy, it is installed in a direction in which the main orientation direction is parallel to the longitudinal direction of the surface light source device, similarly to the lens film.
The distance between the CCD camera and the sample surface was set to 1 m in a vertical state, and the CCD camera was moved on the equator between −70 ° and + 70 ° with respect to the sample surface, and the angular dependence of luminance was measured. Only the start and last pitches were changed by 1 degree, and during that time, the change was made at 3 degree pitches. In the measurement of luminance, the measurement unit was divided into 3 parts in the horizontal direction and 9 parts in the vertical direction, the luminance data of the 9 divided parts in the central part in the horizontal direction were read, and the average brightness of 0 degree (vertical direction) was displayed.
Further, luminance spots were obtained and displayed from the maximum value, the minimum value, and the average value of 9 data at 0 degree by the following formula.
Luminance spots (%) = (maximum value−minimum value) / average value × 100
The inspection surface light source device was installed so that the longitudinal direction was the equator direction.
The surface light source device for inspection was measured after being left in a horizontal state for 1 hour or more after being spotted. The lamp intensity was the maximum value. The measurement was performed in a dark room.

8. Isotropy of brightness variation distribution profile (Isotropic brightness)
The above luminance and luminance unevenness measurement is also performed in the direction orthogonal to the longitudinal direction of the surface light source device for inspection. From the profile diagram of the angle dependency of the average luminance in both directions, it is half of the luminance of 0 degree (vertical direction). The angle at the strength position (half-width angle) was determined. The following ranking was performed based on the value obtained by dividing the smaller value of the half-width angle by the larger value.
Rank 1: 1.0-0.90, Rank 2: 0.89-0.80, Rank 3: 0.79-0.70, Rank 4: 0.69 or less

9. Decrease in luminance at an intermediate angle of the luminance variation distribution profile (decrease in luminance)
The following ranking was performed based on the value obtained by dividing the luminance at an angle of 70 degrees by the luminance at an angle of 45 degrees in the angle dependence profile of the average luminance in both directions obtained by the isotropic evaluation of the luminance distribution profile.
Rank 1: 1.0 or less, Rank 2: 1.1 to 3.0, Rank 3: 3.1 to 5.0, Rank 4: 5.1 or more.
The ranking was determined by the higher value obtained in both directions.

10. Maximum illuminance, isotropy of illuminance, and drop in illuminance in a cold cathode tube type direct surface light source device RISA-COLOR / ONE-II (manufactured by Highland) used for the above luminance characteristics is a variable angle illuminometer Change to ZERO-ONE (manufactured by Highland) to measure the angle dependence profile of the illuminance in the longitudinal direction of the surface light source device for inspection and the direction orthogonal to the direction, and the angle dependence of the obtained illuminance It was obtained by the same method as the luminance measurement from the profile diagram. Ranking was done in the same way.
The distance between the sample surface and the illuminometer was 50 cm in the vertical direction.

11. Appearance defect The brightness condition of the surface of the measurement sample at the time of measuring the brightness and the brightness spots was observed with the naked eye with the observation angle changed in all directions to determine the presence or absence of glare. The case where glare is not visible is indicated by ○, and the case where it is visible is indicated by ×.
Further, the dark room lamp was turned off and the wall surface of the dark room was observed with the naked eye to observe the presence or absence of lightness spots.

12. Melt flow rate of thermoplastic resin Measured under the condition of 2.16 kgf in accordance with JIS K 7210 A method.

(Production example of light diffusion member)
1. Light diffusing member 1
Cyclic polyolefin resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers, melt flow rate: 2.0 (230 ° C.)) 35 parts by mass, ethylene and octene block copolymer resin (INFUSE (made by Dow Chemical) TM) D9817.15 Melt flow rate: 26 (230 ° C)) 65 parts by mass was melt mixed at a resin temperature of 250 ° C using a PCM45 extruder manufactured by Ikekai Tekko Co., Ltd. The light diffusion layer made of the above resin composition is laminated by laminating on the surface of the polyester film while passing the polyester film (thickness of 50 μm), and pressing the cooling roll with a pressure roll made of silicone rubber and cooling. Polyester film base To obtain a diffusing member 1. The characteristics are shown in Table 1. The light diffusion layer thickness was 100 μm.

2, light diffusion member 2
Using two melt extruders, 35 parts by mass of polycarbonate resin (Lexan (TM) EXL1810T (SABIC Innovative Plastics Co., Ltd. melt flow rate: 35 (300 ° C.))) and TPX resin (first extruder) DX350 made by Mitsui Chemical Co., Ltd. Melt flow rate: 110 (280 ° C.) 65 parts by mass as a light diffusion layer, with a second extruder, polypropylene adhesive resin (Admer (TM) QE060 made by Mitsui Chemicals, Inc.) Heat cohesive layers are laminated on both sides with a total thickness of 400 μm by melt coextrusion with a T-die method and cooling with a mirror cooling roll so that the rate is 7.0 (230 ° C.). A light diffusing member 2 was obtained.
The characteristics are shown in Table 1. The film was adhered to the cooling roll at the time of cooling using a vacuum chamber. The layer thickness configuration was 30/140/30 (μm).

3, light diffusion member 3
Using two melt extruders, 35 parts by mass of a cyclic polyolefin resin (TOPAS (TM) 6013S-04 Topas Advanced Polymers melt flow rate: 2.0 (230 ° C.)) in the first extruder Block copolymer resin composed of ethylene and octene (INFUSE (TM) D9817.15 melt flow rate: 26 (230 ° C.), manufactured by Dow Chemical Co., Ltd.) 65 parts by mass is used as a light diffusion layer. -Type adhesive resin (Admer (TM) SE800 manufactured by Mitsui Chemicals Co., Ltd., melt flow rate: 5.7 (190 ° C.)) is melt-coextruded by a T-die method so that both surfaces become layers, By cooling, a light diffusing member 3 in which a heat adhesion layer was laminated on both surfaces having a total thickness of 56 μm was obtained. The characteristics are shown in Table 1. The film was adhered to the cooling roll at the time of cooling using a vacuum chamber. The layer thickness configuration was 8/40/8 (μm). The extrusion temperature of the first extruder was 230 ° C., and the second extruder temperature was 250 ° C.

4. Light diffusion member 4
Polypropylene resin (Sumitomo Chemical Co., Ltd., Sumitomo Nobrene FS2011DG3) 50 parts by mass, ethylene butene copolymer (Mitsui Chemicals, Tuffmer A0585X) 30 parts by mass and nanocrystal structure control type polyolefin elastomer resin (Mitsui Chemicals, Notio PN3560) A kneaded polyolefin resin composition obtained by melt-extruding 20 parts by mass of a biaxial extruder in advance with a resin temperature of 240 ° C. in a 60 mmφ single screw extruder (L / D; 22). After being melt-mixed and extruded with a T-die, it was cooled with a casting roll at 20 ° C. to obtain an unstretched sheet. Next, this unstretched sheet was stretched 4.5 times at a stretching temperature of 118 ° C. using a difference in roll peripheral speed of a longitudinal stretching machine, and further stretched 8.2 times at 145 ° C. in the transverse direction at 158 ° C. Heat set. Subsequently, corona treatment was performed on one surface thereof to obtain a light diffusion member 4 having a thickness of 25 μm. The characteristics are shown in Table 1.

5, light diffusion member 5
(1) Production of crystalline homopolyester resin (M1) When the temperature of the esterification reaction can was reached and reached 200 ° C., from terephthalic acid (86.4 parts by mass) and ethylene glycol (64.4 parts by mass) The resulting slurry was added and antimony trioxide (0.017 parts by mass) and triethylamine (0.16 parts by mass) were added as catalysts while stirring. Next, the pressure was increased and the pressure esterification reaction was performed under the conditions of a gauge pressure of 3.5 kgf / cm ² and 240 ° C. Thereafter, the inside of the esterification reaction vessel was returned to normal pressure, and magnesium acetate tetrahydrate (0.071 parts by mass) and then trimethyl phosphate (0.014 parts by mass) were added. Further, the temperature was raised to 260 ° C. over 15 minutes, and trimethyl phosphate (0.012 parts by mass) and then sodium acetate (0.0036 parts by mass) were added. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction can, gradually heated from 260 ° C. to 280 ° C. under reduced pressure, and subjected to a polycondensation reaction at 285 ° C. until a predetermined intrinsic viscosity was reached. went.

  After completion of the polycondensation reaction, filtered with a NASRON filter with a filtration particle size of 5 μm (initial filtration efficiency: 95%), extruded into a strand from a nozzle, and preliminarily filtered (pore size: 1 μm or less) It was cooled and solidified, and cut into pellets. The obtained crystalline homopolyester resin (M1) has a crystal melting heat of 35 mJ / mg, a melting point of 256 ° C., an intrinsic viscosity of 0.56 dl / g, a melt viscosity of 91 Pa · s, an Sb content of 144 ppm, and an Mg content. The amount was 58 ppm, the P content was 40 ppm, the color L value was 56.2, and the color b value was 1.6. Further, inert particles and internally precipitated particles were not substantially contained.

(2) Production of copolymer polyester resin (M2) Intrinsic viscosity comprising 100 mol% terephthalic acid unit as the aromatic dicarboxylic acid component, 70 mol% ethylene glycol unit and 30 mol% neopentylglycol unit as the diol component Of 0.59 dl / g and a melt viscosity of 121 Pa · s were produced in accordance with the production method of (M1).

(3) Polystyrene (M3)
A polystyrene resin (PS) having a melt viscosity of 147 Pa · s was used.

(4) Preparation of coating solution (M4) Dimethyl terephthalate (95 parts by mass), dimethyl isophthalate (95 parts by mass), ethylene glycol (35 parts by mass), neopentyl glycol (145 parts by mass), zinc acetate (0.1 Parts by mass) and antimony trioxide (0.1 parts by mass) were charged into a reaction vessel, and a transesterification reaction was performed at 180 ° C. over 3 hours. Next, 5-sodium sulfoisophthalic acid (6.0 parts by mass) was added and the esterification reaction was performed at 240 ° C. over 1 hour, and then at 250 ° C. under reduced pressure (10 to 0.2 mmHg) for 2 hours. The polycondensation reaction was carried out to obtain a copolyester resin having a number average molecular weight of 19,500.

  7.5 parts by mass of a 30% by mass aqueous dispersion of the obtained copolyester resin and 11.3 parts by mass of a 20% by mass aqueous solution of a self-crosslinking polyurethane resin containing an isocyanate group blocked with sodium bisulfite. The organic tin catalyst was mixed in an amount of 0.3 parts by weight, 39.8 parts by weight of water and 37.4 parts by weight of isopropyl alcohol.

  Furthermore, 0.6 parts by mass of a 10% by mass aqueous solution of a fluorine-based nonionic surfactant, 2.3 parts by mass of a 20% by mass aqueous dispersion of colloidal silica (average particle size 40 nm) as particles A, and dry as particles B 0.5 parts by mass of a 3.5% by mass aqueous dispersion of method silica (average particle size 200 nm, average primary particle size 40 nm) was added. Next, the pH of the coating solution is adjusted to 6.2 with a 5% by weight aqueous sodium bicarbonate solution, and the solution is precisely filtered with a felt type polypropylene filter having a filtration particle size (initial filtration efficiency: 95%) of 10 μm. Adjusted.

(5) Production of surface light diffusing polyester film As raw materials for the light diffusing layer, 57 parts by mass of crystalline homopolyester (M1), 38 parts by mass of copolymerized polyester (M2), and 5 parts by mass of polystyrene (M3) were each 135. After drying under reduced pressure (1 Torr) at 6 ° C. for 6 hours, the mixture was mixed and supplied to the extruder 2. Further, 76.7 parts by mass of crystalline homopolyester (M1) and 23.3 parts by mass of copolymerized polyester (M2) as raw materials for the support layer (A) were each dried under reduced pressure (1 Torr) for 6 hours, and then mixed. It was supplied to the extruder 1.

  Supplied from Extruder 2 and Extruder 1 with a set temperature of 275 ° C. up to the melting section, kneading section, polymer pipe, gear pump and filter of each extruder and 270 ° C. set temperature of the polymer pipe after the filter. Each raw material was laminated using a two-layer merging block and melt-extruded into a sheet form from the die.

  In addition, the thickness ratio of the (A) layer and the (B) layer was controlled using the gear pump of each layer so that it might become 90:10. In addition, a stainless sintered body filter material (nominal filtration accuracy: 95% cut of 10 μm particles) was used for each of the filters. The temperature of the die was controlled so that the temperature of the extruded resin was 275 ° C.

  The extruded resin was brought into close contact with a cooling drum having a surface temperature of 30 ° C. using an electrostatic application method, and solidified by cooling to prepare an unstretched film. At this time, the layer surface (A) was a surface in contact with the cooling drum. The take-up speed of the unstretched film by the cooling drum was 12 m / min.

  The obtained unstretched film was heated to 79 ° C. using a preheating roll, and stretched 3.4 times in the longitudinal direction between rolls having different peripheral speeds. At this time, the temperature of the film was monitored with an infrared radiation thermometer, and the heater temperature was controlled so that the maximum temperature of the film was 100 ° C.

After completion of the longitudinal stretching, the obtained uniaxially stretched film was cooled to 50 ° C., and then the coating liquid (M4) was applied to one side (A layer side) of the film. The coating solution was controlled so that the wet coating amount was about 15 g / m ² . Thereafter, the coated surface was dried in a drying furnace.

  The both ends of the uniaxially stretched film having the coating layer are gripped with clips, guided to a tenter, preheated to 120 ° C., stretched 2.5 times in the transverse direction at 135 ° C., and then 1.6 times in the transverse direction at 140 ° C. The film was stretched twice, further heat treated at 240 ° C. for 10 seconds, and subjected to a relaxation treatment of 3.3% in the transverse direction in the process of cooling to 60 ° C., thereby producing a light diffusion member 5 having a total thickness of 100 μm. The characteristics are shown in Table 1.

6. Light diffusing member 6
Using two melt extruders, a polypropylene resin FLX80E4 (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Noblen, melt flow rate: 7 (230 ° C.)) is supplied as a base layer using a first extruder as a base layer, and a second layer is used as a surface layer. Supply polypropylene adhesive resin (Mitsui Chemicals Co., Ltd., Admer QF551, melt flow rate: 5.7 (230 ° C.)) with an extruder, melt coextrusion by T-die method, and then surface of satin The light diffusion member 6 having a thickness of 80 μm was obtained by cooling with a 50 ° C. cooling roll. The characteristics are shown in Table 1. The film was adhered to the cooling roll at the time of cooling using a vacuum chamber. Both the first extruder and the second extruder were uniaxial, and both outlet temperatures were 250 ° C. The surface temperature of the cooling roll was set to 50 ° C. The film was wound up at a speed of 21 m / min. The layer thickness configuration was 11/57/11 (μm).

7. Light diffusing member 7
In the manufacturing method of the light diffusing member 6, the light diffusing member 7 was obtained by the same method as that of the light diffusing member 6 except that the mirror roll was replaced with a cooling roll and the surface temperature was set to 20 ° C. The characteristics are shown in Table 1.

8. Light diffusing member 8
Kimotosha light up film 100UK2 was used. The characteristics are shown in Table 1.

9. Light diffusion member 9
On one side of a 100 μm thick highly transparent polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.), 50 parts by mass of spherical acrylic resin particles (Toughtick (TM) FH-S300 manufactured by Toyobo Co., Ltd.) having an average particle size of 3 μm; The light-diffusion member 9 was obtained by apply | coating and drying using a coating machine so that the mixing part of 50 mass parts of polyurethane resins might be 30 micrometers in thickness after drying. The characteristics are shown in Table 1.

10. Light diffusing member 10
On one side of a highly transparent polyester film (Cosmo Shine A4300, manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm, 7.0% by weight of polyester resin prepared by the following method and organic particles having an average particle size of 2.0 μm (benzoquaminamine formaldehyde condensate) ) 4.0 wt%, antistatic agent (cationic quaternary ammonium salt) 0.32 wt%, water as a solvent 50 wt%, IPA (isopropyl alcohol) 40 wt% in dry weight After applying and drying by a reverse roll method so as to be 1.0 g / m ² , heat treatment was performed at 160 ° C. for 30 seconds to form a light diffusion layer, thereby obtaining a light diffusion member 10. The characteristics are shown in Table 1.
(Preparation of copolymer polyester)
In a stainless steel autoclave equipped with a stirrer, thermometer and partial reflux condenser, 747 parts of terephthalic acid, 664 parts of isophthalic acid, 202 parts of sebacic acid, 58 parts of fumaric acid, 744 parts of ethylene glycol, 720 parts of neopentyl glycol 720 The esterification reaction was carried out from 160 ° C. to 220 ° C. over 3 hours. Next, 0.7 part of tetra-n-butyl titanate was added, and the temperature was raised from 200 ° C. to 220 ° C. over 1 hour to carry out an esterification reaction. Next, the temperature was raised to 255 ° C., the pressure of the reaction system was gradually reduced, and the mixture was reacted for 1 hour 30 minutes under a reduced pressure of 0.22 mmHg to obtain a copolyester. The obtained polyester had a weight average molecular weight of 20,000 and was pale yellow and transparent.

11. Light diffusing member 11
In the manufacturing method of the light diffusing member 9, the light diffusing member 11 was obtained by the same method as the manufacturing method of the light diffusing member 9, except that the diffusion layer thickness was changed to 35 μm. The characteristics are shown in Table 1.

12. Light diffusion member 12
A polycarbonate resin-based light diffusion plate (Panlite (TM) 65HLW 1.5 mm) manufactured by Teijin Chemicals Ltd. was used. The characteristics are shown in Table 1.

(Production example of lens film body)
1, lens film 1
A lens structure was formed on one side of a highly transparent polyester film (Cosmo Shine A4300, manufactured by Toyobo Co., Ltd.) having a thickness of 188 μm by the following method to prepare a lens film 1.
After the transfer, a plate having the following lens structure was prepared.
The lens structure is such that the base length is 75 μm, the top length is 25 μm, the angle between the base and the hypotenuse is 45 degrees, and the base length is 25 μm, the angle between the base and the hypotenuse. Takes a structure in which a triangular prism of 45 degrees is formed. The crossing angle between the trapezoidal prism and the triangular prism was 90 degrees.
Using the prepared plate, the lens structure was subjected to UV transfer molding using a UV curable resin on one side of a highly transparent polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.) to obtain a lens film 1. The characteristics are shown in Table 2.

2, lens film 2
A lens structure was formed on one side of a highly transparent polyester film (Cosmo Shine A4300, manufactured by Toyobo Co., Ltd.) having a thickness of 188 μm by the following method to prepare a lens film 2.
After the transfer, a plate having the following lens structure was prepared.
In the lens structure, triangular prisms having a base length of 50 μm and an angle between the base and the hypotenuse of 45 degrees are arranged at a pitch of 75 μm with a gap of 25 μm, and the length of the base is 25 μm so as to fill the gap. In this structure, a triangular prism having an angle of 45 degrees between the base and the hypotenuse is formed. The angle of intersection of the two triangular prisms was 90 degrees.
Using the prepared plate, the lens structure was subjected to UV transfer molding using a UV curable resin on one side of a highly transparent polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.) to obtain a lens film 2. The characteristics are shown in Table 2.

3, lens film 3
A transparent acrylic photocurable resin composition (manufactured by Daicel Cytec Co., Ltd., trade name “PETIA”) is applied to one side of a highly transparent polyester film (Cosmo Shine A4300 manufactured by Toyobo Co., Ltd.) having a thickness of 188 μm, and rolled gold The lens film 3 molded in a form in which hemispherical dome-shaped protrusions having a height of 25 μm and a diameter of 50 μm are closely packed is obtained by an ultraviolet molding method in which the mold is molded and irradiated with ultraviolet rays. . The characteristics are shown in Table 2.

4. Lens film 4
In the manufacturing method of the lens film 3, the lens film 4 was obtained in the same manner as the lens film 3 except that the lens structure was changed to a prism structure having an apex angle of 90 degrees, a prism height of 25 μm, and a prism base width of 51 μm. The characteristics are shown in Table 2.

(Example 1, Example 2, and Comparative Examples 1-3)
The first light diffusing member (A) is limited to the light diffusing member 1, the second light diffusing member (C) is limited to the light diffusing member 5, and the lens film (B) is of the type shown in Table 3 with the above-mentioned cooling function. The front luminance and luminance spots were evaluated according to the luminance and luminance spot measuring method in a cathode ray tube type direct surface light source device. The evaluation is performed so that the opposite surface of the lens surface of the lens film (B) and the first light diffusing member (A) are in contact with each other, and the lens surface of the lens film (B) and the second light diffusing member (C) are in contact with each other. In addition, the lower light diffusion member side was installed on the transparent acrylic plate of the surface light source device.
The first light diffusion member (A) is overlaid in the direction in which the light diffusion layer is in contact with the lens film (B), and the second light diffusion member (C) is overlaid in the direction in which the opposite surface of the light diffusion layer is in contact with the lens film (B). It was.
The lens film (B) was installed so that the main light distribution direction was parallel to the longitudinal direction of the cold cathode tube.

FIG. 8 shows the relationship between the center surface particle size (SGr) of the lens surface of the lens film (B), front luminance, and luminance unevenness using the numerical values in Table 3. The higher the central surface particle size (SGr) of the lens surface of the lens film (B), the higher the front luminance and the lower the luminance unevenness. The above hypothesis has been proven. In addition, it has been shown that an unexpected effect of suppressing luminance unevenness is also exhibited.
Moreover, the fall of a brightness | luminance is suppressed by using a lens film (B) with a small fall of emitted light intensity. Further, by using a highly isotropic lens film (B), it is possible to enhance the isotropic luminance (comparison of Example 1, Example 2 and Comparative Example 2).

(Comparative Example 4)
In the method of Example 1, the overlapping order of the light diffusing member 1 and the lens film 1 is changed so that the opposite surface of the lens surface of the lens film 1 is a transparent acrylic plate on the transparent acrylic plate of the surface light source device. It evaluated by the method similar to Example 1 except having changed so that it might install so that the light-diffusion member 1 might be installed on the lens surface of this lens film 1, and to contact.
The front luminance was 7430 Cd / m ² and the luminance unevenness was 5.8%.
Compared with the method of Example 1, both the front luminance and the luminance unevenness are significantly inferior.

(Comparative Example 5)
In the method of Example 1, it evaluated by the method similar to Example 1 except changing the installation direction of the lens film 1 so that a lens surface may contact | connect the light-diffusion member 1. FIG.
The front luminance was 1680 Cd / m ² and the luminance unevenness was 13.5%.
Compared with the method of Example 1, both the front luminance and the luminance unevenness are significantly inferior.
From the above, it is shown that the light diffusion laminate can exhibit the effect of the present invention for the first time in the configuration of the present invention, and can achieve both high front luminance and low luminance unevenness.

(Examples 3-7 and Comparative Examples 6-10)
In the method of Example 1, brightness and brightness spots were evaluated by the same method as in Example 1 except that the second light diffusing member (C) was changed to that shown in Table 4.
The results are shown in Table 4 together with Example 1.

  If the second light diffusing member (C) is not laminated, an appearance defect will occur. When the second light diffusion member (C) is not laminated, the surface glossiness of the lens film surface is as high as 172% (Comparative Example 10).

FIG. 9 shows the relationship between the total light transmittance / parallel light transmittance ratio of the second light diffusing member (C), the front luminance, and the surface glossiness, using the numerical values in Table 4.
The surface glossiness is measured on the surface of the light diffusion layer of the laminated body laminated so that the lens surface of the lens film (B) and the opposite surface of the light diffusion layer of the second light diffusion member (C) are in contact with each other. The measured value was displayed.
It can be seen that both high front luminance and low surface gloss can be achieved only in the range of an appropriate ratio of total light transmittance / parallel light transmittance. It is also shown that these relationships are critical.
By reducing the surface glossiness, appearance defects can be improved. Therefore, it can be said that the appearance defect can be improved while maintaining high front luminance by setting the total light transmittance / parallel light transmittance ratio of the second light diffusing member (C) within the range of the present invention.

(Example 8, Example 9 and Comparative Examples 11-15)
In the same method as in Example 1, the luminance measurement was switched to the above-described illuminance measurement, and the angle dependency profile of the illuminance was measured by the above-described method for the combination of optical members shown in Table 5, and the obtained illuminance Frontal illuminance, drop in illuminance, and isotropy of illuminance were evaluated from the angle dependence profile diagram. In addition, appearance defects and luminance spots were evaluated. For the luminance spots, the case where the value of the luminance spots obtained by the above-described method was less than 4% was judged as ◯, and the case where it was 4% or more was judged as x.
The results are shown in Table 5.

  From the results of the above Examples and Comparative Examples, it is shown that the effect of the present invention is remarkable in the illuminance as well as the luminance.

(Example 10, Example 11 and Comparative Examples 16-20)
Regarding the system of combinations of optical members shown in Table 6, a flutter-type light source (four in 100 mm square) is a direct surface light source device using a special LED light source prototyped by Opto Design Co., Ltd. The LED illuminants were arranged at equal intervals, and front illuminance, illuminance drop, illuminance isotropy, appearance defect, and flutter pattern concealment were evaluated in the same manner as in Example 8.
The results are shown in Table 6.

The flutter pattern concealment is determined by observing the light-emitting surface with the naked eye in the lighting state and observing the visibility of the flutter light-control pattern image. did.
From these Examples and Comparative Examples, it is shown that the effect of the present invention is also remarkable in the flutter type surface light source device.

(Example 12, Example 13, and Comparative Examples 21-25)
For the combination system of optical members shown in Table 7, the surface light source device is replaced with a light guide plate of a dot printing method in which LED light sources are arranged on two sides facing each other at 300 mm square, and the front illumination intensity is obtained in the same manner as in Example 8. The illuminance drop, the isotropic illuminance, the appearance defect, and the dot shielding properties were evaluated. The dot concealment property was determined by observing the surface light source device from directly above in the lighting state, and determining that the dot of the light guide plate was not visible as “◯” and the case of being visible as “X”. In addition, the distance between the sample surface and the illuminometer was evaluated as 100 cm in the vertical direction. The dot concealment property was determined by observing the light output surface with the naked eye in the lighting state and observing the visibility of the dot for controlling the light output of the light guide plate.
The results are shown in Table 7.

  It can be seen that the effect of the present invention is remarkable even when a light source of a light guide plate type is used.

The light diffusion laminate of the present invention includes a first light diffusion member having a light diffusion degree having a specific structure and characteristics, a lens film having a specific structure and specific characteristics, and a second light diffusion having a specific light diffusion degree. When the surface light source device is composed of a combination of members and is used in a surface light source device, it is installed on the light output side of the surface light source device, so that high light output efficiency and uniformity of light output efficiency are improved. And higher brightness, and uniformity of illuminance and brightness can be improved.
In addition, since the lens film of the present invention has a specific structure and specific characteristics, the emitted light appearing in a mountain range type structure oriented in one direction such as a commonly used prism lens film or lenticular type is in a specific direction. The so-called condensing phenomenon is a decrease in the isotropy of the distribution profile of the outgoing light and the drop in the outgoing light intensity that appears around 45 degrees in the angular dependence of the outgoing light. It can be suppressed in a maintained form. Therefore, when the surface light source device of the present invention is used for general illumination, uniform illumination with little directivity can be achieved.
Further, by laminating a light diffusing member having a specific light diffusivity on the lens surface of the lens film, the lens structure of the lens film maintains the high illuminance and luminance characteristics that are the effects of the present invention. Problems with appearance defects such as glare on the light-emitting surface caused can be improved. Therefore, the light diffusion laminate of the present invention can be suitably used for lighting devices.

Claims (4)

A first light diffusing member (A) comprising at least one layer composed of a mixture of at least two kinds of resins that are incompatible with each other; a lens film (B) having a lens structure formed on one side; and a second light diffusing member ( The lens surface of the lens film (B) and the second light diffusing member (C) are in contact with each other, and the opposite surface of the lens surface of the lens film (B) is in contact with the first light diffusing member (A). In the light diffusing laminate, the first light diffusing member (A) and the lens are arranged so that the surface on the first light diffusing member (A) side is in contact with the surface on the light emitting surface side of the surface light source device. The film (B) and the second light diffusion member (C) satisfy the following (i) to (iii):
(I) The first light diffusing member (A) has a total light transmittance / parallel light transmittance ratio of 8 to 110,
(Ii) The lens surface (Gr) has a center surface particle size (SGr) of 5000 to 30000 μm ² and an incident angle of 45 degrees in the variable-angle light distribution profile of the emitted light when incident at 0 degree. Satisfy simultaneously that the drop in the luminous intensity is 3.0 or less,
(Iii) The total light transmittance / parallel light transmittance ratio of the second light diffusing member (C) is 1.0 to 30.   2. The light diffusion laminate according to claim 1, wherein the surface glossiness of the surface of the laminate on the second light diffusion member (C) side is 5 to 80%.   3. A surface light source device, wherein the surface of the light diffusing laminate according to claim 1 is installed such that the surface on the first light diffusing member (A) side is in contact with the surface on the light exit surface side of the surface light source device. .   An illumination device comprising the surface light source device according to claim 3.