KR20090025107A - Prism sheet having wet-out property and lcd back light unit thereby - Google Patents

Abstract

A prism sheet having a high wet-out property and a liquid crystal display device using the same are provided to easily exhaust moisture remaining on a light guide plate by forming a flat floor surface and a fixed slope in a ridge line of a plurality of unit prisms included in a prism sheet. A base film(100) has a flat single-surface(101). A light refraction part(120) is formed in the other surface of the base film faced with the flat single-surface by arranging a plurality of unit prisms(110) having a predetermined cross-sectional shape toward a specific direction. The base film is made of material like a glass, a metal thin film, and a transparent synthetic resin of polyethylene, polypropylene, and polycarbonate etc. The light reflection part is used in order to reflect a light passing through the base film. The unit prisms are used in order to reflect a light radiated in the base film toward the specific direction. The light reflection part including the unit prisms is integrally formed with the base film. A ridge line of the unit prisms has a slow curve.

Description

Prismatic sheet with excellent water dissipation with curved ridges and liquid crystal display using the same {Prism sheet having wet-out property and LCD back light unit}

The present invention relates to a prism sheet and a liquid crystal display backlight unit using the same, and more particularly, the ridge lines of a plurality of unit prisms included in a prism sheet used in a conventional backlight unit for a liquid crystal display device are uniform with a flat bottom surface. The present invention relates to a prism sheet having a structure of easily discharging moisture present in a light guide plate by having an inclination and a liquid crystal display backlight unit using the same.

In general, a liquid crystal display device refers to a device in which a liquid crystal, which is a liquid and a solid intermediate material, is injected between two glass substrates formed of electrodes to display a number or an image by applying an electric field.

Since the liquid crystal display device is not a self-luminous device, it should have a back light unit as a light source for generating light, and the panel portion in which liquid crystals are uniformly arranged in the light generated by the backlight unit. Displays the image while adjusting the light transmission amount.

6 is an exploded perspective view illustrating a backlight unit of a conventional liquid crystal display.

As shown in FIG. 6, the conventional LCD backlight unit 1 includes a light source 2, a reflector 3, a light guide plate 4, a diffusion sheet 5, a prism sheet 6, and a protective sheet 7. And, these components are assembled integrally by a case (not shown).

Although the light source 2 can be used as the first light emitting part in the liquid crystal display device, there are many kinds of light sources 2. Generally, the light source used in the liquid crystal display device has a low power consumption and emits very bright white light. (Cold Cathode Fluorescence Lamp) is used.

A light guide plate 4 is formed on the lower side of the LCD panel 8 and on one side of the light source 2, and converts spot light generated from the light source 2 into surface light to convert the light to the front surface. It serves to project.

A reflector plate 3 is formed on the rear side of the light guide plate 4 and serves to reflect light from the light source 2 toward the front LCD panel 8.

A diffuser sheet 5 is formed on the upper surface of the light guide plate 4 and serves to uniformize the light emitted through the light guide plate 4.

The prism sheet 6 is used to increase brightness by refracting and condensing light that diffuses in both horizontal and vertical directions as the light passes through the diffusion sheet 5 and the brightness drops sharply. Two prism sheets arranged in the vertical direction are used.

The protective sheet 7 is located on the top of the prism sheet 6 to prevent scratches of the prism sheet 6, and the moiré phenomenon occurs when using the prism sheet 6 formed in two layers in the vertical and horizontal directions. Used to prevent effects.

The members of the above-described backlight unit are laminated by being bonded or bonded to each other and assembled by being sealed in a high vacuum state by a case (not shown).

However, when the backlight unit is assembled with the panel, moisture may penetrate between the gaps of the case during long-term use, or moisture may penetrate during the sealing process. Refraction or diffusion may occur to act as a cause of lowering visibility or light concealment of the backlight unit.

Since most of the members constituting the backlight unit have a flat structure on both sides of the stacked units, it is difficult to form a structure for discharging moisture in these members.

Accordingly, the present invention relates to a technique for facilitating the discharge of water present in the backlight unit by adding another technical concept to the prism sheet 125 having the uneven prism pattern on one surface of such components. .

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a prism sheet having a function of facilitating the discharge of moisture present in a backlight unit.

Another object of the present invention is to provide a liquid crystal display backlight unit using the prism sheet.

Technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the present invention is a plurality of units having a predetermined cross-sectional shape integrally with the base film on the other surface of the base film opposite to the flat surface on a transparent base material having a flat one surface A photorefractive portion is formed in which prisms are arranged in one direction, and a ridgeline of the unit prism constituting the light refraction portion is formed in an irregular curve to provide a prism sheet.

According to the prism sheet according to the embodiment of the present invention, it is possible to manufacture a prism sheet having a light refraction function and a discharge capacity of moisture present in the backlight unit, and the luminance value, transmittance, and haze value are almost the same as those of the conventional prism sheet. It is possible to manufacture the liquid crystal display backlight unit that can minimize the stains caused by the excellent discharge capacity of the water present therein, and further forms a light diffuser on the prism sheet having excellent discharge capacity. By doing so, it is possible to omit the diffusion sheet used in the related art, resulting in a reduction in manufacturing cost and a thickness of the back light unit.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In this process, the thickness of the lines or the size of the components shown in the drawings may be exaggerated for clarity and convenience of description.

In addition, terms to be described later are terms defined in consideration of functions in the present invention, which may vary according to a user's or operator's intention or custom.

Therefore, definitions of these terms should be made based on the contents throughout the specification.

1 is a perspective view showing a prism sheet according to an embodiment of the present invention.

As shown in FIG. 1, the prism sheet 10 according to the embodiment of the present invention is based on the base film 100 having the flat one surface 101, and faces the flat one surface 101. On the other surface of the base film 100, the light refracting portion 120 in which a plurality of unit prisms 110 having a predetermined cross-sectional shape are arranged in one direction is formed.

The base film 100 is a base layer of the prism sheet, and is generally made of a transparent material such as transparent synthetic resin such as polyethylene, polypropylene, polycarbonate, glass, or other metal thin film.

Although the thickness of the base film 100 is not specifically limited, The thing of a micrometer (micrometer) unit is mainly used.

The light refracting unit 120 is a member for refracting light passing through the base film 100 to have a predetermined orientation, and is formed on the other surface of the base film 100.

On the other side of the base film 100 is formed a light refracting portion 120 is composed of a plurality of unit prisms 110 for refracting the light emitted from the base film 100 in a predetermined direction.

However, FIG. 1 illustrates a light refracting portion 120 having a triangular cross-section as a unit prism 110 and a triangular prism-shaped unit prism. The cross-sectional shape of the constituting unit prism 110 is not limited to a triangle, and is a transparent object having at least two optical planes capable of refracting light, such as a semi-circle shape (also called a semi-cylinder shape or a lenticular shape) and a trapezoid shape. As long as at least one pair of surfaces of the optical plane is a shape capable of refracting non-parallel light, all of the surfaces can be applied to the present invention.

In addition, in the application of the prism sheet 10 of the present invention in detail, what kind of cross-sectional shape of the prism 110 is arranged depends on the characteristics of the device actually applied, the required angle, and other screen sizes. It depends on the matter.

The optical refraction unit 120 including the plurality of unit prisms 110 is integrated with the base film 100, and specifically, the optical refraction index is applied to the base film 100 by compression molding a film used as the base film 100. The unit 120 is formed.

The ridge line 102 of the unit prism 110 constituting the light refraction portion 120 has a gentle curve, and is formed with irregular height in a predetermined range. The ridge 102 has a predetermined curvature and changes irregularly to form a water discharge space.

In this case, the ridge line 102 is defined as a line connecting the highest point, that is, the vertex, in the cross section of one unit prism 110.

Ridges 102 may include one or more high or low points LP as they vary irregularly. Here, the high point HP means a point where the height of the ridge increases and then decreases, and the low point LP means a point where the height of the ridge decreases and then increases.

One ridge may include one high point or one low point and may include several high and low points.

The ridge line 102 of the unit prism 110 is designed to be changed to an irregular curve as described above. The prism sheet 10 of the present invention is a protective film on the prism sheet 10 when the prism sheet 10 is laminated as a member of the backlight unit of the liquid crystal display device. Alternatively, when a member, such as a polarizing film, is laminated, a gap is secured between the members to be stacked to smoothly discharge moisture present in the backlight unit through the gap.

In Fig. 1, the high point and the low point formed by the change of the ridge lines do not overlap with each other on the basis of the entire plurality of unit prisms, and the arrangement is preferably arranged irregularly.

The reason why the position of the high point or the low point should be irregularly arranged without overlapping between the unit prisms 110 is that a new pattern is generated by placing the high point H or the low point L adjacent to each other inside the prism sheet 10. This is to suppress the unwanted refraction of light generated.

2 is a view showing various forms of the side of the unit prism according to an embodiment of the present invention.

(a) shows a unit prism 21 (∪-shaped ridgeline) in which the ridge includes one low point, and (b) shows a unit prism (22, ∩-type ridgeline) in which the ridge includes one high point. Indicates

(c) shows the unit prism 23 including one low point and one high point.

As shown in FIG. 1, the unit prism has a constant pitch P and the ridge lines change into irregular curves.

Here, the height of the ridge lines is preferably changed within the range of 30% to 200% of the pitch P of the unit prism. If the height of the ridge line is out of the above range, the water discharge performance may be improved, but the luminance uniformity may be lowered.

In addition, it is preferable to limit the difference between the highest point and the lowest point in the ridgeline within 50% of the unit prism pitch P. This is because the overall luminance uniformity can be lowered even when the height change is excessive in one unit prism.

Here, the highest point means the highest point among the starting point, the end point, and the included high point of the unit prism, and the lowest point means the highest point among the starting point, the end point and the lowest point of the unit prism. do.

In the case of (a), the highest point is H2 and the lowest point is H1, so H2-H1 must be within 50% of the unit prism pitch (P), and in case of (b), H3-H4 is the unit prism pitch (P). In the case of (c), H5-H6 should be within 50% of the unit prism pitch (P).

If the height change rate is not limited, the overall optical characteristics may be degraded. Therefore, the height of the ridge lines is changed irregularly, but the change in height is preferably limited to 50% of the pitch.

The ridgeline is preferably formed in an irregular curve, but the radius of curvature in the curve is preferably three times or more the pitch P. If the radius of curvature is too small, there is a risk of sudden change in the height to degrade the optical properties.

FIG. 3 shows a prism sheet composed of unit prisms having a ridge line having one high point, and FIG. 4 shows a prism sheet composed of unit prisms having a ridge line having one low point.

As shown in FIG. 1, a prism sheet may be formed by mixing a unit prism having a high point and a unit prism having a low point, or as shown in FIGS. 3 and 4, as a unit prism having only a low point. The prism sheet may be configured by a unit prism having only a high point.

In this case, it is preferable that the positions of the low point and the high point are irregularly distributed over the entire optical refraction portions 320 and 420. This is because when a high point or a low point is collected at a specific position, a new pattern may occur.

Referring to FIG. 3, the plurality of unit prisms 310 constituting the optical refraction unit 320 are arranged in one direction, and are preferably formed to be in close contact with each other without being separated from each other, but require straightness rather than refractive index of light. In this case, a spacing plane may be provided between the unit prisms 310. That is, the unit prisms 310 may be disposed at a predetermined distance (spaced plane) without densely arranging each other.

Preferably, the height of the unit prism 310 is 5 to 500 μm, and when the cross-sectional shape of the unit prism 310 is triangular, the vertex angle θ is preferably 30 to 120 °.

FIG. 5A is a view illustrating a case in which a light diffuser pattern for providing light diffusivity is introduced in addition to the light refractive property of the prism sheet of the present invention, and FIG. 5B is an enlarged view of part “A” of FIG. 5A. .

5A and 5B, the light diffuser (see 520 of FIG. 5A) may have a lower end portion of the light refraction portion 520, that is, a lower end portion of a valley portion formed between neighboring unit prisms 510. Are irregularly distributed in the shape of a lens such as a circle, an ellipse, or a form in which they are mixed.

The light diffuser 530 covers the surface of the light refraction portion 320 while having a plurality of lens-shaped irregularities having a rounded surface at the lower end of the unit prism 510, or having a predetermined distance.

At this time, the size of the elliptical lens shape of the light diffuser 530 should be smaller than the size of the light refractive portion. Specifically, when the light diffuser 530 is a circular lens, the size ratio of the diameter / prism pitch (P) of the lens In the case where the light diffuser 530 is an elliptical lens, the ratio of the long radius / prism pitch P of the lens is 0.01 to 0.9, and the height ratio of the height / light refractive portion of the light diffusion region is 0.01 to 0.9.

The reason for having the numerical range as described above is a value in consideration of the diffusion effect and the light refractive characteristics of the diffusion region.

The light diffuser 530 has a small amount of light passing through the base film 500 and the light refraction portion 520 on the surface of the light refraction portion 520. It is formed to diffuse, while maintaining the inside and outside to spread as much as possible.

The light diffuser 530 is preferably distributed at least 50% or more in the valley surface between the unit prisms 510 that is less than half the height h of the height h of the unit prisms 510 constituting the light refraction portion 520. Do.

The reason for having the above distribution density is that the prism sheet of the present invention is manufactured using a mold having an opposite shape, that is, a mold having an intaglio, wherein the surface of the mold having a shape opposite to that of the light refractive portion 520 is provided. When the sandblasting process is used, the acid part of the mold is damaged a lot. When the prism sheet is manufactured using the mold thus treated, the acid part of the mold becomes the bone part of the prism sheet. As a result, the light diffuser 530 is concentrated on the valley of the formed prism sheet.

5A and 5B, the light diffusing body 530 has a circular shape. However, the light diffusing body 530 has an elliptical lens or a mixture of a circular lens and an elliptical lens. It may be

In general, the optical refraction portion 520 is formed by pressing a mold having a negative prism shape on a transparent film having a predetermined thickness so that an embossed prism shape corresponding to the negative prism is formed on the surface of the transparent film. In this case, the upper surface of the transparent film is a light refractive portion 520 having a prism shape, and the lower surface is a base film 500.

Therefore, in order to simultaneously form the light refracting portion 520 and the light diffusing body 530 in the manufacturing process of such a prism sheet as described above, irregularities are formed on the surface of the negative prism shape of the mold. When the pressing process is performed using the above, the optical refraction unit 520 and the light diffusing body 530 as described above may be manufactured with the prism sheet.

The prism sheet described above is used by being stacked on the surface from which light is emitted from the light guide plate, and by using a prism sheet in which the light diffuser 530 is formed as described above, a diffusion sheet may be omitted. have.

However, the prism sheet of the present invention can be used regardless of an edge type in which a light source is disposed on the side of the light guide plate, and a direct type in which the light source is disposed below the light guide plate of the light guide plate of the liquid crystal display device. In addition, any kind of light source may be used regardless of CCFL, LED, and the like.

Hereinafter, when manufacturing the light guide plate using the prism sheet according to the embodiments of the present invention, the haze value (haze: meaning the spread of light), transmittance, and moisture dissipation are excellent without a large decrease in luminance. Listen and explain. However, the content not described herein is omitted because it can be inferred technically sufficient by those skilled in the art.

1. Experimental Example and Comparative Example

Experimental Example

A prism sheet including one low point was formed on the curved ridges of the plurality of unit prisms formed on the upper layer of the base film.

At this time, in the prism sheet, the vertex angle of each unit prism is 90 °, the pitch is 60 mu m, the height of the starting point of the unit prism is 30 mu m, and the height of the bottom is about 28 mu m on the average, and the position of the neighboring low point is The prism sheet was manufactured so that the height difference between the highest point and the lowest point was about 2 占 퐉 (3.3% of the pitch) as a prism sheet distributed randomly without overlapping.

Comparative Example

In the prism sheet, each unit prism had a straight ridge line, a vertex angle of 90 degrees, a pitch of 60 μm, and a height of unit prism ridge line of 30 μm.

2. Measurement of physical properties

(1) Measurement of surface luminance

The central luminance of the prism sheet produced by comparison was compared with the above experimental example using TOPM's BM-7. The backlight unit used for this monitor is 170EU-L31.

(2) Haze value and permeability measurement

Using the NHD 5000W, the prism-shaped surface was placed on the lower part of the detector, and the measurement was performed by matching the direction of the prism with the detector.

(3) Water discharge capacity measurement

In the BLU 154X3-L06 model for notebooks using two prism sheet structures, the prism sheets of the above experimental and comparative examples were cut so that the prism directions were perpendicular to each other, and the lower layer portion was perpendicular to the backlight unit, and the upper layer portion was The prism direction was assembled in the horizontal direction of the backlight unit, and stored for 96 hours in a constant temperature and humidity chamber, and then observed that there was no problem in appearance.

At this time, the constant temperature and humidity conditions are 60 ℃, 75% humidity conditions.

3. Property measurement result and analysis

Table 1 shows the results for the measured physical properties measured above.

Referring to Table 1, when the prism sheet is manufactured to have a constant inclination and inclination change point on the ridge of the unit prism as in the experimental example of the present invention, the difference in the center luminance, transmittance, and haze value is almost different from that of the comparative example. It was found that does not exist.

On the other hand, in the prism sheet according to the experimental example of the present invention, even when stored for a long time in a humidity condition of about 75%, the dew condensation or the plane light of the backlight unit due to this did not occur, This proves that the prism sheet of the present invention has a very good water discharge capacity.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings and tables, the present invention is not limited to the above embodiments, but may be manufactured in various forms, and common knowledge in the art to which the present invention pertains. Those skilled in the art can understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Therefore, the true technical protection scope of the present invention will be defined by the claims below.

1 is a perspective view showing a prism sheet according to an embodiment of the present invention,

2 is a view showing various forms of the side of the unit prism according to an embodiment of the present invention,

3 is a perspective view showing a prism sheet composed of unit prisms having a ridge line having one high point;

4 is a perspective view showing a prism sheet composed of unit prisms having a ridge line including one low point;

5A is a perspective view illustrating a case in which a light diffuser pattern for providing a light diffusivity is introduced in addition to the light refractive index of the prism sheet of the present invention;

5B is a partially enlarged perspective view illustrating an enlarged portion “A” of FIG. 5A;

6 is an exploded perspective view showing a backlight unit of a conventional liquid crystal display device.

Explanation of symbols on the main parts of the drawings

10: prism sheet 100, 300, 400: base film

102, 302, 402: ridges 110, 310, 410: unit prism

120, 320, 420: light refractive portion HP: high point

LP: Low P: Unit Prism Pitch

Claims (18)

A base film of a transparent material having a flat one surface; On the other surface of the base film opposite to the flat one surface is formed a light refracting portion in which a plurality of unit prisms having a predetermined cross-sectional shape are arranged in one direction integrally with the base film, The prism sheet of the unit prism constituting the optical refraction portion is formed in an irregular curve to secure a water discharge space. The method of claim 1, The ridge line is a prism sheet, characterized in that formed in an irregular curve in the range of the height corresponding to 30% to 200% of the unit prism pitch. The method of claim 1, The difference between the highest value and the lowest value of the height of the ridge line is a prism sheet, characterized in that within 50% of the unit prism pitch. The method of claim 1, The ridge line has a radius of curvature of three times or more the pitch of the unit prism, and is irregularly changed. The method of claim 1, And the ridge has one or more high or low points. The method of claim 5, wherein The high point and the low point are prism sheet, characterized in that irregularly distributed over the entire optical refractive portion. The method of claim 1, The ridgeline of the unit prism is a prism sheet, characterized in that the shape of the shape of the fin. The method of claim 1, Prismatic sheet, characterized in that the material of the base film is a transparent synthetic resin. The method of claim 1, The cross-sectional shape of the unit prism is one of the triangle, semi-circular, trapezoidal diffuser prism sheet, characterized in that. The method of claim 1, And the plurality of unit prisms are continuously formed without being separated from each other. The method of claim 1, A prism sheet, wherein a spaced plane is formed at a predetermined interval between the plurality of unit prisms. The method of claim 1, If the cross-sectional shape of the unit prism is a triangle, the vertex angle of the diffuser prism sheet, characterized in that 30 ° to 120 °. The method of claim 1, A prism sheet, wherein a light diffuser for diffusing light in valley portions between neighboring unit prisms is integrally formed with the unit prism, and the light diffuser is irregularly distributed in the valley surface of the unit prism. . The method of claim 13, The light diffuser is a diffuser prism sheet, characterized in that 50% or more is distributed in the valley surface of less than half the height of the unit prism height. The method of claim 13, The light diffuser is a circular lens shape, the diameter of the lens shape is a diffuser prism sheet, characterized in that the size of 0.01 to 0.9 times the unit prism pitch. The method of claim 13, The light diffuser has an elliptical lens shape, and the long radius of the lens shape is 0.01 to 0.9 times the unit prism pitch. Light guide plate; A light source disposed on the side or the back of the light guide plate: and And a prism sheet of claim 1 formed on a surface on which light is emitted from the light guide plate. A panel unit including an upper substrate on which a color filter is formed and a lower substrate on which a TFT is formed; A liquid crystal display device comprising the backlight unit of claim 17 disposed under the lower substrate.

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