## Description 

## BACKGROUND OF THE INVENTION 

Field of the Invention 

[0001] The present invention relates to a laser irradiation device that roughens the surface of a member to enhance adhesiveness on the surface of the member and relates to a surface roughening method using the same. 

Background Art 

[0002] When a given memberisattached toan objectwith adhesive,roughening isgenerallyperformed forthe surface of the member as pretreatment. For example, as the "roughening" treatment, a variety of techniques are generally used as follows: a method using sandpaper, sandblasting, water blasting, and chemical treatment. 

[0003] However, the respective techniques have posed the following drawbacks: the method using sandpaper is of a contact type, and hence, has caused fluctuations in quality of the roughened surface; sandblasting has posed dust- related problems on working environment; and water blasting and chemical treatment have required draining facilities. 

[0004] In view of the above, roughening treatment using a laser beam has been developed to solve the drawbacks described above. This roughening treatment is of a non-contact type, whereby fluctuations in quality of the roughened surface can be inhibited. Simultaneously, this roughening treatment neither pose any problems on working environment nor require draining facilities. 

[0005] Forexample,as described in Japan Laid-open Patent Application Publication No. S62-103317,there has been developed a technology for irradiating the surface of a member made of metal or so forth with a short-wavelength laser beam or a long-wavelength laser beam in order to roughen the surface of the member. 

[0006] However,when the surface ofa memberisroughened to enhance adhesiveness on the surface of the member, chances are that adhesiveness on the member surface is not necessarily enhanced and is rather degraded by simply increasing the intensity of the laser beam or by simply increasing the number of irradiated laser beams per unit area on the member surface. 

[0007] Besides, it is also concerned that a laser diode, provided for generating a laser beam, is undesirably damaged by simply increasing the intensity of the laser beam. 

[0008] The present invention has been produced in view of the drawbacks described above. It is an object of the present invention to provide a laser irradiation device and a surface roughening method using the same, whereby it is made possible to irradiate a laser beam optimal to perform roughening for the surface of a member in order to enhance adhesiveness on the member surface, and simultaneously, a laser diode, even when used as a light source of the laser beam, can be mitigated in damage. 

## SUMMARY OF THE INVENTION 

[0009] According to an aspect of the present invention, a laser irradiation device is provided that roughens a surface of a member by irradiating a laser beam on the surface of the member so as to enhance adhesiveness on the surface ofthe member.The laserirradiation device ischaracterizedin thatthelaserbeamisirradiated atintervalsofpredetermined time, and the laser beam at one time of irradiation has a waveform including a former portion and a latter portion. In the former portion, an increase rate of irradiation intensity per unit time is maximized on an outset of irradiation and is gradually reduced as the irradiation intensity approaches a maximum. In the latter portion, a reduction rate of irradiation intensityperunittime ismaximized aftertheformerportion and isgraduallyreduced asthe irradiation intensityapproaches a baseline current. 

[0010] Preferably, the laser irradiation device is characterized in that the waveform of the laser beam at one time of irradiation further includes an intermediate portion in which the increase rate of irradiation intensity per unit time ap- proaches zero. The intermediate portion is formed between the former portion and the latter portion. 

[0011] According to another aspect of the present invention, a surface roughening method is provided that irradiates a laser beam on a surface of a CFRP member by the laser irradiation device described above so as to enhance adhe- siveness on the CFRP member. 

[0012] Preferably, the surface roughening method further includes the following steps: irradiating a plurality of laser beams that include the laser beam and are aligned in a row; and irradiating the plurality of laser beams on the surface of the CFRP member at intervals of predetermined time by moving the laser irradiation device in a moving direction orthogonal to the row of the plurality of laser beams. The surface roughening method is characterized in that a ratio of a longitudinal interval size to a longest diameter is greater than or equal to 25% and less than or equal to 800%, where the longest diameter is defined as a moving directional length of each of recesses formed by irradiating the plurality of 

